Many of the first homes in SF were made of wood and easily caught on fire. So in the early 1800s, firefighters put these all around the city to have easy access to water. The city stopped making them many years later when fire hydrants and city wide pipes were installed. BUT after the 1906 earthquake, many pipes and hydrants were damangef and unhelpful in fighting off the fires the quake created. So the city reinvested in cisterns as a back up method in case of another quake. There are now ~200