And the fact that Las Vegas resembles a gaudy neon mirage in the desert? Well, surely, no more apt image could apply to a place where dreams — of riches, risks, romance — often go to die.

But Las Vegas is also a place where dreams, large and small, are just as frequently born. Hotel and casino owners dream of founding (or furthering) their financial empires. Singers, dancers, comedians and magicians dream of performing night after night before rapt crowds. The unemployed from all over the U.S. dream of finding work. After all, in the first decade of the 21st century, only one or two American cities grew at a faster pace than Las Vegas. And while the foreclosure crisis of the past few years has hammered Nevada’s biggest city, the bright lights and (seemingly) endless stream of cash are still powerful lures for visitors and would-be Las Vegans alike.

In 1955, 50 years after Las Vegas was founded, LIFE magazine took a rather skeptical look at the boomtown and its prospects for growth in a cover story titled “Gambling Town Pushes Its Luck.” The Loomis Dean images in this gallery, meanwhile — many of which were never published in LIFE — provide some wonderful visual reminders of just how raw a place Las Vegas was in the mid-’50s, before the Rat Pack made the city its home away from home and decades before it would begin to reinvent itself as a family-friendly mecca.

Some of the pictures appeared in the June 20, 1955, issue of LIFE, in an article that described the city as “set for its biggest boom,” with some caveats:

At Las Vegas last week the temperate was up to a torrid 110 degrees and the townsfolk who operate the only large gambling center in the country welcomed the seasonable weather. With it they expected the usual bountiful summer crop of tourists trying out their luck and leaving their money behind. The sign of good times seemed everywhere … But with all this a shadow of doubt fell across Las Vegas, a worry that the boom it was set for has started to wilt.

In the past month, two new top-notch hotels opened. One was the $5 million Dunes, which lugged 120 slot machines in anticipation of the rush. The other was the Moulin Rouge, the first interracial hotel in Las Vegas, which welcomed back whites and Negroes to its accommodations and gambling tables. It had Joe Louis as part-owner and host, and a lively, lovely chorus in its floor show.

Like a gamble on a prolonged winning streak, Las Vegas had the feeling its run of luck couldn’t end. For more than a decade, it had parlayed one prosperous year into a more prosperous next year and went into the expansion more in the spirit of hunch than of calculated economics. The opening of the new hotels and of what Las Vegas hoped would be a new era of money-making was opulent and promising … But when the excitement of the opening died down, the town looked at its new places were customers were scarce and the betting light and wondered: Had Vegas pushed its luck too far?

That question, of course, has come up repeatedly over the years, as the desert city has steadily grown from a 100-acre (40 hectare) railroad town in 1905 to a sprawling metropolis of close to 2 million people today. But no matter the odds, Las Vegas always seems to have one more ace in the hole, one more trick up its sleeve to keep the lights on, the casino floors humming and the dreamers coming back again and again.

But back in 1948, a number of inspired amateur craftsmen — not content with riding mundane, conventional bicycles — took their enthusiasm to another, unlikely level and … well, let’s let LIFE tell it, in the words the magazine used in its December 27, 1948, issue:

“To Webster a bicycle is ‘a light vehicle having two wheels, one behind the other.’ Such a definition theoretically describes the contraptions [seen in the article], but fails to do justice to the imagination of the Chicago chapter of the National Bicycle Dealers’ Association.

“By artfully applying welders’ torches to metal tubing, the chapter’s members transform ordinary, utilitarian bicycles into traveling monstrosities. By far the most outlandish ideas have come from the Steinlauf family, who produced from their bicycle repair shop most of the oddities [shown in the article]. They are hazardous; generally at least one member of the clan is to be found in the hospital.”

Here, LIFE.com offers a selection of photos of these preposterous creations from six long decades ago — mechanistic marvels that belie the famous old saying (which we just made up) that there’s no such thing as a useless bicycle.

Of the indispensable photographs taken during the Second World War, Margaret Bourke-White’s image of survivors at Buchenwald in April 1945 — “staring out at their Allied rescuers,” as LIFE magazine put it, “like so many living corpses” — remains among the most haunting. The faces of the men, young and old, staring from behind the wire, “barely able to believe that they would be delivered from a Nazi camp where the only deliverance had been death,” attest with an awful eloquence to the depths of human depravity and, maybe even more powerfully, to the measureless lineaments of human endurance.

What few people recall about Bourke-White’s survivors-at-the-wire image, however, is that it did not even appear in LIFE until 15 years after it was made, when it was published alongside other photographic touchstones in the magazine’s December 26, 1960, special double-issue, “25 Years of LIFE.”

Pictures, meanwhile, from Buchenwald, Belsen and other camps that LIFE did publish — made when Bourke-White and her colleagues accompanied Gen. George Patton’s Third Army on its legendary march through a collapsing Germany in the spring of 1945 — were among the very first that documented for a disbelieving American public the wholly murderous nature of the camps. (At the end of this gallery, see how the original story on the liberation of the camps appeared in the May 7, 1945, issue of LIFE, when the magazine published a series of brutal photographs by Bourke-White, William Vandivert and other LIFE staffers.)

LIFE photographer Margaret Bourke-White

Here, on the anniversary of the April 11, 1945, liberation of Buchenwald, LIFE.com presents a series of Bourke-White photographs, the majority of which never ran in the magazine, from that notorious camp located a mere five miles outside the ancient, picturesque town of Weimar, Germany. Her justifiably iconic picture of men at the Buchenwald fence suggests the horrors made manifest by the Nazi push for a “final solution”: the Bourke-White photographs here, on the other hand, do not suggest, or hint at, the Third Reich’s horrors; instead, they force the Holocaust’s nightmares into the unblinking light.

In Dear Fatherland, Rest Quietly — her devastating 1946 memoir, subtitled “A Report on the Collapse of Hitler’s ‘Thousand Years’” — Bourke-White recalls the ghastly landscape that confronted the Allied troops who liberated Buchenwald, and her own tortured response to what she, the troops from the Third Army and her journalist peers witnessed and recorded there:

There was an air of unreality about that April day in Weimar, a feeling to which I found myself stubbornly clinging. I kept telling myself that I would believe the indescribably horrible sight in the courtyard before me only when I had a chance to look at my own photographs. Using the camera was almost a relief; it interposed a slight barrier between myself and the white horror in front of me.

This whiteness had the fragile translucence of snow, and I wished that under the bright April sun which shone from a clean blue sky it would all simply melt away. I longed for it to disappear, because while it was there I was reminded that men actually had done this thing — men with arms and legs and eyes and hearts not so very unlike our own. And it made me ashamed to be a member of the human race.

The several hundred other spectators who filed through the Buchenwald courtyard on that sunny April afternoon were equally unwilling to admit association with the human beings who had perpetrated these horrors. But their reluctance had a certain tinge of self-interest; for these were the citizens of Weimar, eager to plead their ignorance of the outrages.

In one of the signal moments of his long career and, indeed, of the entire war, an enraged General Patton refused to recognize that the Weimar citizens’ ignorance might be genuine — or, if it was genuine, that it was somehow, in any moral sense, pardonable. With Olympian wrath, Patton ordered the townspeople to bear witness to what their countrymen had done, and what they themselves had allowed to be done, in their name.

Margaret Bourke-White’s pictures of these terribly ordinary men and women — appalled, frightened, ashamed amid the endless evidence of the terrors that their compatriots had long unleashed — Bourke-White’s pictures remain among the most unsettling she, or any photographer, ever made. Long before the political theorist Hannah Arendt introduced her notion of the “banality of evil” to the world in her 1963 book, Eichmann in Jerusalem, Margaret Bourke-White had already captured its face, for all time, in her photographs of “good Germans” forced to confront their own complicity in an unfathomably barbarous age.

— Ben Cosgrove is the Editor of LIFE.com

Credit: Alfred Eisenstaedt

But in color photos taken before and after the invasion, LIFE’s Frank Scherschel captured countless other, lesser-known scenes from the run-up to the onslaught and the heady weeks after: American troops training in small English towns; the French countryside, implausibly lush after the spectral landscape of the beachheads; the reception GIs enjoyed en route to the capital; the jubilant liberation of Paris itself.

As presented here, in masterfully restored color, Scherschel’s pictures feel at-once profoundly familiar and somehow utterly, vividly new.

NOTE: Information on the specific locations or people who appear in these photographs is not always available; Scherschel and his colleagues simply did not have the means to provide that sort of data for every single one of the thousands of photographs they made. When the locale or person depicted in an image in this gallery is known, it is noted in the caption.

From her earliest days as an actress until late in her career — when she had, against her will, been cast in the public eye as the century’s ultimate Sex Goddess — Marilyn posed for LIFE magazine’s photographers. Many of those pictures never ran in LIFE magazine.

The negatives for the revelatory images seen here were discovered during the years-long effort to digitize LIFE’s immense, storied photo archive — an archive that includes outtakes and entire photo shoots that, for reasons as varied as the subjects they covered, were never published.

Here, then, is a series of stunning shots of the one and only Marilyn, as well as some possible explanations why the pictures never made it into print.

Here, on Mother’s Day weekend, LIFE.com offers a selection of portraits of famous moms (Jackie Kennedy, Shirley MacLaine) with their kids, famous kids (Liz Taylor, Sophia Loren) with their moms and, in a few instances, famous kids with their famous moms.

[See TIME.com's "Top 10 Movie Moms We Wish Were Ours."]

The focus of the gallery, however, is most decidedly not meant to suggest that famous moms are any more worthy of notice than any other mothers anywhere in the world who feed, clothe, encourage, protect, challenge and, ultimately, unconditionally love their kids. Instead, the focus of this gallery is, quite frankly, a simple acknowledgement that, like most everybody else, we’re more or less fascinated by fame.

“Let me tell you about the very rich,” F. Scott Fitzgerald once wrote. “They are different from you and me.” An observation to which he might well have added: “And the famous? They’re a whole lot stranger.”

But whether rich or famous (or neither); whether strange or perfectly, unpretentiously, refreshingly normal, moms deserve recognition simply because, after all — as all of us will readily admit in our more brutally honest moments — moms rule the world. And while devoting one measly day a year to celebrating and honoring mothers everywhere might be a rather feeble way to express our gratitude and love, not to worry. They’re moms. They understand.

Still … would it kill you to pick up the phone once in a while?

Like William Blake’s admonition to “see a world in a grain of sand,” Cartier-Bresson’s defining aim has been summed up in the notion of (in the English translation) “the decisive moment” — that is, the fraction of a second when a living tableau presents itself to a photographer, and he or she must rely on both instinct and experience to know when to make the picture, to get the shot.

That Cartier-Bresson routinely cut up — literally cut up, into pieces, with scissors — his contact sheets and discarded those pictures that did not come close to capturing a decisive moment hardly lessens or cheapens the scope of the man’s singular and still, today, almost overwhelming achievement. But the practice of ruthlessly culling weak images from the strong does, perhaps, provide insights into the admirably unsentimental nature of an artist like HCB — and perhaps nowhere was this lack of undue sentiment more striking than in Cartier-Bresson’s color photography.

There’s a reason, it turns out, why coming across his color photos can be so jarring; not only did Cartier-Bresson infrequently shoot in color, but he destroyed virtually all of his color negatives, leaving the almost exclusively black-and-white legacy familiar to most photography fans. Finding out that Cartier-Bresson shot professionally in color — and sometimes worked on major, long-term assignments in that format — is the sort of unexpected revelation than provides the student of photography with not only a surprise, but a sudden sense of enlargement.

One of Cartier-Bresson’s most significant color projects was a 1958 assignment for LIFE: a four-month, 7,000 mile tour through communist China during that country’s convulsive “great leap forward,” when the huge, ancient nation was being alternately pushed and pulled, dragged and harried by its leaders to leave its past behind and to embrace industrialization, collectivism and the precepts of Chairman Mao. (“The staggering Chinese upheaval … goes on,” LIFE wrote of the ‘great leap,’ “spurred by the biting fury that Mao himself expressed when he declared, Communism is not love, Communism is a hammer we use to destroy the enemy.”)

“With the perceptiveness for which he is famous,” LIFE declared of the photographer’s work in China, “Cartier-Bresson has shown how the Chinese individually react and live amid the oppressive regimentation imposed on them.”

Whether or not viewers today see what LIFE told its readers they would encounter in that issue in early 1959, what remains clear in the pictures presented here, in both color and in black and white, is that decades into his long, varied career Cartier-Bresson was still seeking and still finding those never-to-be-repeated decisive moments.

Ask 20 random people, “What is the nature of time?” and chances are pretty good that you’ll get 20 disparate answers born of a thousand different factors, from a respondent’s cultural background to the mood he or she happens to be in when asked the question. Time is an arrow, says one. Time is a circle, suggests another. Time is relative. Time is an illusion. Time is whatever we imagine it to be.

But no matter how assured or unhesitating the reply, most people would be hard-pressed to offer a single, definitive method for illustrating time. A clock face is too prosaic; a pendulum is too arbitrary; a gravestone is too … gravestoney. How on earth can we capture what is essentially a philosophical concept like time (or, if you prefer, Time, with a capital T) using a purely practical method or mechanism like, say, photography?

Pablo Picasso "draws" with light, 1949

In honor of the idea of Daylight Savings Time — a practice that, in effect, adds a bit more daylight into most everyone’s routine — and fully aware that the true nature of time remains, and will likely always remain, an unknowable mystery, LIFE.com offers a selection of marvelous photographs, stroboscopic and otherwise, by the great Gjon Mili. (At left: Mili’s famous 1949 portrait of Pablo Picasso creating what LIFE magazine called a “distorted spatial centaur” in midair with a small flashlight.) Here are technically brilliant pictures that fiddle with moments, junctures, sequences — and in the process offer a playful commentary on the slippery relationship between mere mortals and the temporal.

“To see a world in a grain of sand,” William Blake famously wrote, “and a heaven in a wild flower, hold infinity in the palm of your hand and eternity in an hour.” At their best, Gjon Mili’s stroboscopic photographs not only mirror Blake’s vision, but celebrate — with an unsentimental, clear-eyed wonder — the reality of sentient beings moving through both space and time.

Seen 60 and even 70 years after they were made, they also remain incredibly cool.

George Lazenby, 1967

In 1967 LIFE sent photographer Loomis Dean to the final casting sessions for On Her Majesty’s Secret Service, and the magazine published a handful of those photos. But some of the choicest frames — Bond wannabes suiting up, holding guns, drinking martinis, wooing women — never ran in the magazine. Here, LIFE.com presents photographs from those auditions, featuring the five top candidates — including the man, George Lazenby (left), who would eventually win the coveted part.

Critical reception of On Her Majesty’s Secret Service has hardly been uniform. There was much initial grumbling, for example, about Lazenby’s performance — especially in light of Connery effectively defining the role for a generation of moviegoers. But the years have been kind to the 1969 flick: Entertainment Weekly, for example, ranks On Her Majesty’s Secret Service the sixth best of the entire franchise, which by 2012 includes more than 20 feature films and is the second highest-grossing film series of all time, behind Harry Potter.

The song, of course, was “Happy Birthday,” and Marilyn’s breathy, intimate rendition — sung, as if the two of them were utterly alone, to President John F. Kennedy — has been celebrated, analyzed and lovingly parodied countless times in the five decades since that indelible prformance. But beyond the buzz that Marilyn’s “Happy Birthday” generated — including, of course, tossing fuel on the already smoldering rumors about an affair between the movie star and the president — the moment, captured from above by photographer Bill Ray in his iconic picture of Monroe, played a key role in the legends that eventually grew around both the actress and JFK. Marilyn, after all, died less than three months later; Kennedy was assassinated the following fall. For stargazers and dusty old historians, alike, the night that Marilyn sang to JFK remains an uncanny, once-in-a-lifetime collision of sex, politics, power and pop culture.

[WATCH: Bill Ray discusses how he got his famous shot of Marilyn, as well as other memories from that now-legendary evening in New York half-a-century ago.] 

“For most people my age,” remembers Ray, who was 26 in 1962, “Kennedy was a god. We were so relieved to have a young, good-looking person in the White House after Eisenhower.”

Of the setup for the birthday gala that night in the Garden, Ray recalls that “all of the photographers were in front in the beginning of the show, but it was another one of these events where security says, ‘Hey, we’re really glad you came. Take a few pictures — and get your ass out!’ The Secret Service started clearing everybody out after a few shots. I was afraid of being held in a cattle pen with the rest of the photographers, so I got away and started moving around the Garden on my own.”

Trying to find an angle from which he might be able to get both Marilyn and JFK in the same frame, Ray moved higher and higher up in the Garden. He had made his way on to a catwalk, literally up among the building’s girders, when the moment that would forever define the evening suddenly arrived.

“It had been a noisy night, a very ‘rah rah rah’ kind of atmosphere,” Ray told LIFE.com. “Then boom, on comes this spotlight. There was no sound. No sound at all. It was like we were in outer space.” Marilyn was onstage, taking off a white fur to reveal that utterly gorgeous, scandalous dress underneath. “It was skin-colored, and it was skin-tight. It was sewn on, covered with brilliant crystals. There was this long, long pause … and finally, she comes out with this unbelievably breathy, ‘Happy biiiiirthday to youuuu,’ and everybody just went into a swoon. I was praying [that I could get the shot] because I had to guess at the exposure. It was a very long lens, and I had no tripod, so I had to rest the lens itself on the railing, and tried very, very hard not to breathe.”

Here, on the 50th anniversary of that night, LIFE.com presents Bill Ray’s unforgettable picture of Marilyn, alone in the spotlight, along with many more photos from the president’s birthday gala at the Garden that were never published in LIFE magazine.

Visit BillRay.com to see more of Bill’s work, and to purchase prints of these and other remarkable photographs.

See TIME.com’s “Happy Birthday, Bombshell” gallery of Marilyn photos.