On the 23d of July, the commodore organized the "California Battalion of Mounted Riflemen." Captain Fremont was appointed major, and Lieutenant Gillespie captain of the battalion. The next day, they were embarked on board the sloop-of-war Cyane, Commander Dupont, and sailed from Monterey for San Diego, in order to land south of the Mexican force, consisting of 500 men, under General Castro, well fortified at a place three miles from the city. A few days afterwards, Commodore Stockton sailed in the Congress for San Pedro, thirty miles from Monterey, and having landed, marched for the Mexican camp. When he arrived within twelve miles of the Mexicans, they fled in small parties, in different directions. Most of the principal officers were afterwards taken, but the mounted riflemen not getting up in time, most of the men escaped. On the 13th of August, Commodore Stockton being joined by eighty riflemen, under Major Fremont, entered the capital of California, Ciudad de los Angeles, or the "City of the Angels." Thus, in less than a month after Stockton's assuming command, the American flag was flying from every commanding position in California, conquered by three hundred and sixty men, mostly sailors.
The form of government established in California, after the conquest, was as follows: The executive power was vested in a governor, holding office for four years unless sooner removed by the President of the United States. The governor was to reside in the territory, be commander-in-chief of the army thereof, perform all the duties of a superintendent of Indian affairs, have a pardoning and reprieving power, commission all persons appointed to office under the laws of said territory, and approve all laws passed by the legislature before they took effect. There was the office of the Secretary of the Territory established, whose principal duty was to preserve all the laws and proceedings of the legislative council, and all the acts and proceedings of the governor. The legislative power was vested in the governor and a council of seven persons, who were to be appointed by the governor at first, and hold their office for two years; afterwards they were to be elected by the people. All the laws of Mexico, and the municipal officers existing in the territory before the conquest, were continued until altered by the governor and council.