Rex's Bar was a dark, somewhat dirty bar that was a setting in the series of Dixon Hill holonovels. This bar, established in 1927, was located across the street from a pharmacy.
The bar was owned by Rex, a friend of the Dixon Hill character. Hill frequently ran up large tabs in the bar which upset the owner and caught Jean-Luc Picard by surprise when he played the role of Hill on the holodeck.
Rex's was also the setting for Lwaxana Troi's brief flirtation with the bar's holographic owner when she was enduring the phase in 2365. (TNG: "Manhunt")
The set of Rex's Bar was located on Paramount Stage 16. ("Manhunt" shooting schedule)