Hard to tell from the picture, but maybe it was the Old Vegas that was later Westworld? Here's a link to a picture of the sign I found online.

http://entertainment.webshots.com/photo/1082152149048217944NWTRgA

The caption underneath reads:

"Old Vegas was an old west themed amusement park that opened up in 1979 as Westworld. It contained a carousel, a mystery mine, a train ride, gunfights, a candy shop, a restaurant and (of course) a casino. The complex was contained by a fort with two towers overlooking the Las Vegas valley. Inside the fort was a western town. The mystery mine caught fire in the 1980s and due to the lack of customers, the fun spot closed in 1987. Old Vegas housing development has built on the property."