Polk Gulch, the microhood surrounding north–south Polk Street, hugs the western edges of Nob Hill and Russian Hill but is nothing like either. It's actually two microhoods: Upper Polk Gulch, fairly classy in its northern section, runs from about Union Street south to California Street; Lower Polk Gulch, the rougher southern part, continues south from California to Geary or so.
Polk Gulch was the Castro before the Castro. It was the city's gay neighborhood into the 1970s, hosting San Francisco’s first pride parade in 1972 and several festive Halloween extravaganzas. The area became known for tranny bars and gay prostitution but has "straightened" out—lost its edge, some would say. Today the friendly saloon the Cinch, the last remnant of gay Polk, and stalwart holdovers from that earlier time—among them folksy Grubstake, where you can get a giant burger until 4 am nightly—share space with newer mid-range restaurants, a passel of bars and nightclubs, and some browsable, funky stores, not to mention two great doughnut shops and the Antique Vibrator Museum.
Downhill and down-market from its hilltop neighbors, Polk Gulch has been flirting with gentrification for almost a decade, but (female) prostitutes still walk the streets of the Lower Gulch, and the neighborhood feels closer in spirit to the Tenderloin, which it borders. Come to see a lively, scrappy, down-to-earth slice of the city that's forever in transition but rarely seems to change.