On August 13, 1846, early in the conflict, U.S. naval forces under Commodore Robert F. Stockton arrived at Los Angeles and raised the U.S. flag without opposition.

[3] The harsh martial law of Captain Gillespie soon ignited a popular uprising among Californios and Mexicans led by General José María Flores beginning on September 22, 1846.

Gillespie's fifty marines were able to resist an initial attack on the government house in town and regrouped on Fort Hill, where they strengthened the fortification with sandbags and mounted their cannon.

Gillespie agreed to withdraw from Los Angeles, under safe passage, on September 30, 1846 on the American merchant ship Vandalia.

The marines were defeated in their attempt at the Battle of Dominguez Rancho, as Stockton's fleet fled south to San Diego.

In December, U.S. Army forces under Captain Stephen W. Kearny were defeated by the Californio Lancers at the Battle of San Pasqual.

On January 12, 1847, to secure the area from future attack, U.S. forces began erecting a 400-foot (120 m) long breastwork on the same strategic site as the previous Fort Hill and named it the Post at Los Angeles.

[13] The enormous old structure made a charming home, which was cut up into suitable parlors and bedrooms and elegantly furnished, with a fine view.

[13] With the growth of the city, however, society moved to newer districts and left the old place to end its days as a rooming house.

The Los Angeles City Council passed a resolution on August 30, 1879, closing the cemetery to any future burials except for those with already reserved plots.

The 238,000 square foot (22,110 m2), $171.9 million facility was designed by the project team of Architect-of-Record HMC Architects and Designer-of-Record Austrian firm Coop Himmelb(l)au.