Upon hearing of the Siege of Los Angeles, on October 4, 1846, Commodore Robert F. Stockton sent U.S. Navy Captain William Mervine and the American ship Savannah to the port of San Pedro to assist Captain Archibald H. Gillespie in military operations. Arriving two days later, Mervine set out on October 7th with sailors, marines and bear flaggers to recapture the town.
The Americans had occupied Los Angeles in August of that year, and residents had hidden some weapons, some by burying them. On August 14, 1846, Pablo Vejar (brother of Juan Nepomuceno Ricardo Vejar) communicated a plan to Maria Casilda Soto (of Rancho La Merced) and Maria Francisca 'Pancha' Perez (wife of ranchero Felipe Lugo), both sympathetic Californio patriots, to hide one of the small ceremonial Plaza cannons used for firing salutes on feast days and other celebrations. Vejar, with the help of Carlos Ballesteros and Jose Domingo Bermudez, transported the old cannon to the peach orchard of Maria Inocencia Reyes. Reyes then buried the cannon in the orchard for safekeeping. The Reyes home adjoined that of Antonio Maria Lugo, located at what today would be the corner of San Pedro Street & 2nd Street. the orchard may have been separate from the property, it was likely adjacent to the Reyes home.
Another slightly different account, from the article “Battle of Dominguez Ranch" by J.M. Guinn, conveys that upon the approach of Stockton and Fremont’s forces in 1846 that Maria Inocencia Reyes’ mother, Maria Clara Cota (with the assistance of her her daughters), buried the cannon in a cane field near their residence on the east side of Alameda Street near First.
On September 27, 1846 when the time had come to put the gun to use, Maria Inocencia Reyes delivered the gun to Jose Dolores de Altagracia “Huero” Higuera, who with the help of a local British carpenter made a cannon carriage from a cart belonging to Louis Vignes.
Mervine's commenced with little knowledge of the terrain or enemy forces. His troops were inadequately armed and they possessed no horses, wagons or cannons. General Jose Flores' force, was similarly equipped with lances, knives and old firearms that had been hidden, but they did have the recently unearthed cannon. This brass four-pounder or pedrero (swivel gun) was described by Jose Francisco de Paula Palomares as bronze and of about six inches in diameter, that it was “mounted over some iron-rimmed carreta wheels, and bound with reatas” and that at length it received the name "Conico".
Mervine and his troops marched on October 7 and reached Dominguez Rancho, where they camped for the night, within view of an advance detachment of Flores' troops. There was some shooting during the night, but with no effect other than keeping Mervine's party on the alert. Then, setting off at daybreak, the American force advanced just to the north of Rancho San Pedro.
The little four-pounder was placed upon the narrow trail that the Americans needed to follow. Ropes were lashed to the limber to quickly pull the gun into the brush for reloading. Californio horsemen deployed at a safe distance from the trail on the enemy flanks. These simple tactics proved effective. When the Americans came within range (about 400 yards), the cannon was fired and quickly pulled back into the brush, followed by covering musket fire from the horsemen.
Mervine's forces were at a disadvantage on foot against an enemy they could neither see nor count. Upon realizing they could not reach Los Angeles, they had no choice but to retreat. The battle lasted less than an hour; and five hours later Mervine's forces were back aboard their ship in San Pedro Bay. Four seriously wounded Americans died and were buried on a little island in San Pedro Bay called Isla de los Muertos (Island of the Dead). Mervine's troops reboarded the Savannah, and after a few days, sailed north to Monterey.