California Admission Day - California 175

Early Mexican–American War, preparations for a planned conflict led to the U.S. Pacific Squadron being extensively reinforced until it had roughly half of the ships in the United States Navy in 1848. Roughly 20% of the US Navy were men of Pan African Ancestry during the Age of Sail.

Since it took 120 to over 200 days to sail from Atlantic ports on the east coast, around Cape Horn, to the Pacific ports in the Sandwich Islands and then the mainland west coast, these movements had to be made well in advance of any possible conflict to be effective.

Initially, with no United States ports in the Pacific, the squadron's ships operated out of storeships that provided naval supplies, purchased food and obtained water from local ports of call in the Sandwich Islands and on the Pacific coast.

Their orders were, upon determining "beyond a doubt" that war had been declared, to capture the ports and cities of Alta California.

Commodore John Drake Sloat, commander of the Pacific Squadron, on being informed of an outbreak of hostilities between Mexico and the United States, as well as the Bear Flag Revolt in Sonoma, ordered his naval forces to occupy ports in northern Alta California.

Sloat's ships already in the Monterey harbor, the USS Savannah, USS Cyane, and USS Levant, captured the Alta Californian capital city in the Battle of Monterey on July 7, 1846, without firing a shot.

Two days later on July 9, USS Portsmouth, which had been berthed at Sausalito, captured Yerba Buena (present-day San Francisco) in the Battle of Yerba Buena, again without firing a shot. On July 29, Sloat transferred his command to Commodore Robert F. Stockton, a more aggressive leader.

The 400 to 650 marines and bluejackets (sailors) of Stockton's Pacific Squadron were the largest U.S. ground force in California. The rest of Stockton's troops were needed to man his vessels.

The 1847 Battle of Santa Clara, the only major engagement to take place in the Bay Area

To supplement this remaining force, Commodore Stockton ordered Captain John C. Frémont, on the U.S. Army Corps of Topographical Engineers survey, to secure 100 volunteers in addition to the California Battalion he had organized earlier. He received 160, exceeding his order.

Volunteers were to act primarily as occupation forces to free up Stockton's marines and sailors. The core of the California Battalion was the approximately 30 army personnel and 30 scouts, guards, ex-fur trappers, Indians, geographers, topographers and cartographers in Frémont's exploration force, which was joined by about 150 Bear Flaggers.

The American marines, sailors, and militia easily took over the cities and ports of northern California; within days they controlled Monterey, San Francisco, Sonoma, Sutter's Fort, New Helvetia, and other small pueblos in northern Alta California. Nearly all were occupied without a shot being fired.