California experienced its first celebration of American Independence Day on July 4, 1847, from a hill overlooking Los Angeles. Early that morning, at sunrise, U.S. occupational troops stationed at Fort Moore,* commanded by 2nd Lieutenant John W. Davidson, 1st U.S. Dragoons, raised the stars and stripes and fired a 13-gun artillery salute. For the sleepy little city (with a population of perhaps only 1,000), the massed artillery fire and American celebration was a new experience.
Six months earlier , Los Angeles had been the last Mexican holdout in Alta California. The Mexican residents of Los Angeles had put up a good fight, but, on January 10, 1847, American forces decisively captured the city a second time, after embarrassingly being driven out the year before. Now, Los Angeles was yet again under American military control and the occupiers appeared determined to stay. Rumors swirled, however, that Mexico forces were coming to again eject the Americans and recapture Alta California.
The rumors had not been lost on the 700-man American garrison in Los Angeles. They wasted no time beginning construction on an earthwork fortification overlooking the city atop of what had become known as Fort Hill. They also erected a 150-foot flag pole from which they proudly flew the stars and stripes over the city. U.S. Army Colonel Jonathan D. Stevenson ordered that an Independence Day celebration be held at the fort. After the flag-raising and artillery salute, city residents approached the fort to watch the event and the American garrison put on a show. The troops formed and paraded before the spectators, read the Declaration of Independence before the assembly, and fired a 21-rifle salute. Perhaps, without fully realizing it, Fort Moore ceremoniously introduced Los Angeles and California to its destiny.
On February 2, 1848, the Treaty of Hidalgo Guadalupe ended the war between Mexico and the United States, ceding all of the Mexican province of Alta California to the United States. Most of Fort Moore’s garrison departed later that year and the fort was fully abandoned by the following year. It was decommissioned in 1853. In 1891, the site was occupied by Los Angeles High School. In 1949, most of the Fort Hill was removed to make way for the new Hollywood Freeway. In 1956, the County and City of Los Angeles, L.A. Department of Water and Power and L.A. Board of Education installed a memorial to the fort, designed by Kazumi Adachi and Dike Nagano (the largest bas-relief military monument in the nation), at 451 North Hill Street. Currently, the Ramon C. Cortines School of Visual and Performing Arts stands on what remains of Fort Hill.
* Named in honor of Captain Benjamin D. Moore, 1st U.S. Dragoons, killed in the Battle of San Pasqual, San Diego County, December 6, 1846. The 400-foot star-shaped fortification was first named “Post at Los Angeles.” The garrison stationed there in 1847 consisted of the Mormon Battalion and 1st Regiment of U.S. Dragoons.
Source: Independence Day, 1847: How Los Angeles Celebrated Its First Fourth by Nathan Masters, Historic California Ports, Camps Stations and Airfields – Fort Moore by Col. Herbert M. Hart, and Fort Moore by Wikipedia.