http://digital.library.unlv.edu/objects/sky/1784
That linked photo depicts the Nevada Turf Club (1959-1960) in the round Quonset hut (formerly the Circus Room, which would later become Barney's Casino), and the Tahoe Plaza Casino (1959-1961), with its distinctive pointed roof and angled corner (which later became Harrah's Recreation Center, and now houses Dotty's Casino, adjacent to the Harrah's parking garage), so that image must be from 1959 or '60.

http://www.thechipboard.com/archives/archives.pl/bid/399/md/read/id/1270226/sbj/the-only-problem-with-this/
As to last year's debate over the Tahoe Palace/Tahoe Plaza building, the color post card (linked above) depicting Harrah's Club and the Tahoe Palace Casino must be from September of 1958, when Frankie Laine and Sue Carson performed at Harrah's Club (their names are on the marquee in the post card).

As to sources, I have spent many hours digging through the newspaper microfilm archives at the Nevada State Library (behind the Capitol in Carson City), and old newspapers are also available online at many subscription sites, such as Ancestry.com and NewspaperArchive.com. When trying to determine the exact date a casino opened, the best source is always a news report written the next morning by the reporter who was actually at the grand opening, or from newspaper reports covering the state gaming commission approving a license for a new club.

This is how I know definitively that the Tahoe Palace Casino was opened by owners of the Reno Palace Club in the summer of 1956, replacing the old Tahoe Colonial Club (Oakland Tribune, June 10, 1956); and on July 1, 1959, some of the same Reno Palace Club owners re-opened the former Tahoe Palace as the new Tahoe Plaza (Reno Evening Gazette, July 2, 1959), which was sold to Harrah's in the fall of 1961 (Nevada State Journal, September 15, 1961).

Newspapers, written the day after something happens, are always more accurate and reliable than some chip collector's blog, an interview with an old-timer who vaguely remembers something from four decades earlier, or unsourced Wikipedia articles. Many recent chip collector guides merely copy other collector guides regarding dates, which are based on old books (such as Harvey J. Fuller's "Index of Nevada Gambling Establishments") that are full of extrapolations, interpolations, and conjecture based on vague, ambiguous state records, not actual eye-witness reports from the date a casino opened.

-- Phillip L. Sublett