Though he has never said it's based on a particular city, given Frank Miller's love of noir (Hollywood influence) and the genesis of the comic during the gritty 1990s while he was living in Los Angeles, it's likely that Los Angeles was the model. Los Angeles is partially a basin city.

While "Sin City" is often colloquially used as a nickname for Las Vegas, Frank Miller's famous neo-noir graphic novel series is actually set in the fictional Basin City. Miller intentionally designed Basin City as a dark, stylized "amalgamation" of several American urban archetypes rather than a direct copy of a single city. However, the influence of Los Angeles and the "hardboiled" detective fiction of the 1930s and 40s is most prominent, particularly in its corrupt police force and sprawling, rain-slicked industrial landscapes. Some fans also point to San Francisco as a visual inspiration for its hills and waterfront "Projects." The nickname "Sin City" in the comics refers to the city's origins as a wild mining camp where the Roark family made a fortune by providing vices to miners. While Las Vegas owns the nickname in the real world, Miller's Basin City is a separate, much more bleak and "noir" environment that exists purely within the dark gutters and stark white silhouettes of the comic's pages.