True! (Well, only some of the movie was filmed there, but more on that in a bit.)
At 56 years old, Atomic Liquor*, located at 917 Fremont St. (just east of Ninth) not only holds Las Vegas' oldest liquor and bar license, but it's still under the original ownership of Joe and Stella Sobchik, now aged 89 and 88, respectively. Wow.
The site's transformation from a café to a bar in 1951 coincided with the first atom-bomb tests at the Nevada Test Site, hence both the name and the market for a bar downtown -- see QoD 05/20/2006 for information on how the mushroom clouds in the desert were marketed as a novel and popular draw for tourists by downtown's hotels and casinos.
For many years Atomic operated 24 hours a day and was popular with everyone from Roy Rogers to members of the Rat Pack; even Barbra Streisand recalls playing pool there in her memoirs. As you mention, with an interior and façade that remain pretty much untouched since opening, the bar was indeed used as a location for certain scenes in the movie Casino, although Dennis, the helpful bartender we spoke with, was unable to confirm which ones specifically. (So, there's a sleuthing mission for a future date ...)
As the downtown area fell into a state of general decline and urban decay in subsequent years, Atomic found itself situated in the midst of a far-from-salubrious neighborhood. The venue suffered from a popularity with dope dealers and hookers and was eventually shut down by Metro for a while, then allowed to reopen with reduced hours (currently 7 am-11 pm daily).
With the whole Fremont East redevelopment project, the area's experiencing something of a resurgence and is less menacing than it has been in recent memory, although we'd still advocate caution if visiting, especially after dark. We haven't been to Atomic in a long time, but from other people's accounts, we gather it's benefited from the changes and is back to being an average-looking dive bar that continues to ignore any marketing opportunities to exploit its historical legacy. You'll find a dusty picture of Sinatra somewhere behind the bar and an age-worn piece of paper that turns out to be the original liquor license, but that's about it. Still, it's worth calling in if you're in the neighborhood and want to experience one of the few remaining authentic slices of Las Vegas history.
And if the '50s is your thing, you'll find another interesting QoD in the archives from almost exactly a year ago (1/11/07, to be precise), when we surveyed other remaining hangouts and icons from the Rat Pack era.
* Although the sign says "Atomic Liquors," everyone seems to refer to it as Atomic Liquor.
