The best-known number in jeans. Levi Strauss moved from Germany to San Francisco in 1853 to start a dry-goods business. His firm diversified into denim trousers in the 1920s, and shrink-to-fit 501s followed. At Levi's flagship store (001 415 501 0100), 300 Post Street in the Union Square shopping district, 501s cost from $49.50 (£33).
The number of inmates killed trying to escape from Alcatraz (seven shot, two drowned). The island (aka The Rock) in San Francisco Bay served as a prison from 1934 to 1963, and was home to the likes of Al Capone. Ferries now run daily from Pier 33 on Fisherman Wharf, and offer tours. Book with the Blue & Gold Fleet (001 415 705 8200; blueandgoldfleet.com), adults from $26 (£18.50).
The year-long "Summer of Love" kicked off in San Francisco on 14 January 1967, when thousands of hippies gathered in Golden Gate Park for a free concert called "Gathering of the Tribes – A Human Be-In". Jefferson Airplane and The Grateful Dead performed; acid guru Timothy Leary said it was time to "turn on, tune in and drop out". The California Academy of Sciences (001 415 379 8000; calacademy.org) is the park's newest attraction, its natural-history museum features a four-storey rainforest. Entrance is $24.95 (£17.80).
The portions of Cherry Garcia ice cream that remained at the Haight-Ashbury branch of Ben & Jerry's by mid-afternoon during Jerry Garcia's memorial party in Golden Gate Park in August 1995. The Grateful Dead frontman is still commemorated in ice cream and "Jerry Jubilee" sundae form at the local "scoop shop", which stands at at 1480 Haight Street (001 415 626 4143; benjerry.com/ haightashbury).
Harvey Milk, the subject of a biopic starring Sean Penn to be released on Friday, was the first openly gay man elected to public office in California. He lasted 323 days before his murder by a disgruntled colleague called Dan White on 27 November 1978. San Francisco is renowned for its gay-friendly attitude, and the 39th San Francisco Pride parade takes place on 28 June (001 415 864 0831; sfpride.org).
The price in dollars of a ride on a cable car, the finest way to navigate the city's hilly topography. The first city cable car ran in 1873. The Cable Car Museum (001 415 474 1887; cablecarmus eum.org) on Mason Street opens from 10am-5pm and is free.
Harvey Milk's campaigning efforts were based at Castro Camera, 575 Castro Street, which became a refuge for young gay men. Just down the road, at number 429, the ornate Castro Theatre (001 415 621 6120; thecastrotheatre.com) hosts the annual Frameline lesbian and gay film festival (001 415 703 8650; frameline.org), 18-28 June.
The price, in pounds, of an off-peak return from Heathrow to San Francisco airport (just off the iconic Highway 101) on British Airways (0844 493 0787; ba.com). Book by 27 January.
The length, in feet, of the Golden Gate Bridge, which, when it opened in 1937, was the longest suspension bridge in the world. It is in fact red – "Golden Gate" refers to the strait it passes over. San Francisco City Guides (001 415 557 4266; sfcityguides.org) offers free guided tours on Sundays and Thursdays at 11am.Reuse content