Most people don't think of casinos when they think of Santa Cruz. Instead, they might think of the boardwalk, hippies, UC Santa Cruz, Birkenstocks, Monterey Bay, the earthquake, etc.
But back in 1904, when the casino was built, it was a main attraction. There was no boardwalk; that was built later around the new casino. The original casino (shown below) burned down in 1906. Work started on a new one in 1907. As far as I know, that building is still part of the current boardwalk, although there is no gambling there. You can read more about the casino and see a picture of it in flames on the Santa Cruz Public library website., along with some pictures of the new casino.
Here's the back of the card, sent to Ida Schack of Chicago in 1905.