Lake Merced was originally christened Laguna de Nuestra Señora de la Merced by Captain Don Bruno de Heceta in 1775. Father Pedro Font, while on the de Anza Expedition to found the Presidio of San Francisco in March, 1776 wrote in his diary, "we saw a grove of live oaks near which is the Laguna de la Merced, where Captain Ribera stopped; and here we saw many bears..." At approximately 11pm of November 22, 1852, a shock was reported to have occurred by those in the areas around the Lake and the following day reports were made that "...a fissure half a mile wide and three hundred yards long was discovered, through which the waters of Lake Merced were flowing to the sea." The most probable cause of the shock was attributed to heavy rains forcing a passage through the sandbank at the north-west. The Lake is reported to have lost 30 feet of water. A map from 1881 shows that the Lake still had a passage to sea, 29 years later. Once owned by Francisco De Haro, first Alcalde of Yerba Buena, as part of the Galindo ranch, the Spring Valley Water Company bought the water rights for the Lake in 1868, and the surrounding watershed in successive years. By purchasing all local supply, the company created a monopoly on San Francisco's water. It was not until 1908, when the city approved construction of O'Shaughnessy Dam creating the Hetch Hetchy Reservoir in the Sierra Nevada mountain range, that the city gained municipal control. Prior to the construction of the dam, Lake Merced was to serve as the city's main reservoir, with plans to expand the lake into land that is now the San Francisco StateUniversity campus. Around this time, Spring Valley sold off some of its land on Lake Merced, making way for the golf courses that exist today. In 1940, Metropolitan Life bought the last of Spring Valley's land to build the Parkmercedapartment complex.
Ecology
The lake is fed by an underground spring, and at one time it did have an outlet to the ocean as shown on an 1869 United States Coast and Geodetic Survey Map. The salt level was always fluctuating, and therefore some species of fish which inhabit the lake are salt and freshwater adapted. There is active recreational fishing at the lake. The lake's water level had been shrinking for decades, endangering the historic role of Lake Merced to support a healthy ecosystem. Due to better management of the aquifer and occasional additions of water, lake level has been rising since 1990.
