The Stonewall Inn was bought by the Mafia and was turned into a gay bar. The bar operated as a "bottle bar," which meant that it was a private club in which patrons were supposed to bring in their own liquor, however the bar illegally sold alcohol. The mafia bribed the NYPD in order to maintain their illegal operation. Stonewall was a safe haven for LGBT+ people who would be denied service or persecuted elsewhere.
Information courtesy of amnewyork.