Those fortunate enough to have lived in San Francisco before the 90s remember when the Presidio was an active US Army base (had been since the gold rush) and only military personnel lived on the 1,500 acres of prime real estate. In fact, the Presidio has been a military post for three different nations since the Spaniards arrived in 1776 and established a small adobe fort just south of the Main Parade Ground (where every day at 5 o-clock the US Army would play the Retreat and fire the cannons). After the National Park Service acquired the land, the Presidio reopened in 1994 as a unique addition to the Golden Gate National Recreation Area. The original adobe fort is now under excavation and every Friday and Saturday 10am-2pm through October 21 members of the public can stop by to watch the archeologists in action and ask questions about their discoveries.
On Sundays in March through October, Off the Grid’s Presidio Picnic turns the Main Parade Ground into an international smorgasbord of local food vendors where thousands gather to enjoy a family (and dog!)-friendly outdoor scene complete with yoga classes, Frisbee, and free bike lessons or craft activities for kids. See https://offthegrid.com/presidio-picnic-faq/ for answers to all your picnicking questions.
A highlight among the many changes made to the Presidio is Crissy Field, which spans most of the waterfront between the St Francis Yacht Club and Fort Point. This former dump and US Air Coast Defense station (also hardly recognizable as the former site of the 1915 Panama-Pacific International Exposition from which only the Palace of Fine Arts remains) was restored to recreate some of the tidal marsh habitat where the Ohlone people harvested shellfish for centuries. A shell mound dating back to 740 AD was found during restoration. The beautifully restored bay-front stretch is now enjoyed by more than 1.2 million visitors per year. For more information about SF’s one-of-a-kind national park visit: http://www.presidio.gov/.