One of the best features of San Francisco is actually what lies just outside the city. Retreating from the urban life, even to pitch a tent for only one night, entails a relatively short car ride, or in some cases a ride across the bay by ferry. One moment you're in the city and suddenly, you're exploring mountains, forests and lakes...watching hawks, sea lions and herons. In addition to easy access, you can depend on the weather staying comfortable between April and October, the local camping season.
The marshland, beaches, forests and bluffs of Point Reyes National Seashore stretch out along the southeastern edge of Marin County and into the bay. Hikers, kayakers and snorkelers will find a bit of everything among Point Reyes' 65,000 acres of wilderness. Folks who explore a bit closer to the Golden Gate can stroll beneath the redwoods and through the oak woodlands in Mt. Tamalpias State Park. A dedicated hike can bring you all the way to the top of Mt. Tam, 2,571 feet above sea level.
If you camp within the 1,640 acres of wilderness in China Camp State Park, you'll probably see some of the old buildings -- remains of a Chinese fishing village at the turn of the century. A ferry brings you to more history on Angel Island, where old army barracks as well as the remains of a Japanese internment camp stand.
The only downside about camping near the city is the crowds. You're not always the only one who wants to make a quick getaway.