From militarymuseum.org:

For half a century, Battery Spencer was one of the most strategically important sites guarding the Golden Gate. Construction started in 1893 and was completed in 1897. Under the provisions of War Department General Order 16, dated 14 February 1902, it was named for Major General Joseph Spencer of the Continental Army, a hero of the Revolutionary War, who died in 1789…In 1917 one gun was removed to rearm Battery Chester at Fort Winfield Scott. The remaining two guns were removed and scrapped in 1943.