Why should you drink in an old bar? Because drinking in really old bars > not drinking in really old bars. Because drinking history > regular history. So without further ado, here are some of the oldest bars in San Diego. You should probably go drink in them.
The building housing the Gaslamp's oldest bar dates back to 1872, and it went through phases of being a boarding house, a feed store, and a blacksmith shop before it became a saloon in 1885. This part of town used to be San Diego's red light district, and the nine apartments above the bar (the Tivoli Towers) were once a brothel with rooms rented by the hour. The wooden bar and back bar are original, and if you walk to the westernmost end of the space, you'll find the bar's first (epic) silver cash register on display.
Fun fact: Famed lawman and San Diego legend Wyatt Earp was an early patron who used to come here to gamble, drink, etc. Some say his spirit never left. Cue the ominous music.