Captain John C. Frémont, leading a U.S. Army topographical expedition to survey the Great Basin, had entered the Sacramento Valley in December 1845.
Frémont's party was at Upper Klamath Lake, Oregon Territory, when it received word that war between Mexico and the U.S. was imminent; the party had then returned to Alta California.
Frémont has reportedly begun agitating American settlers to revolt against Mexican rule.
After telling the Mexican governor and the American Consul Larkin he is merely buying supplies on the way to Oregon, he instead goes to the populated area of California and visits Santa Cruz and the Salinas Valley, explaining he has been looking for a seaside home for his mother.
Mexican authorities become alarmed and order him to leave.
Frémont responds by building a fort on Gavilan Peak and raising the American flag.
Larkin sends word that Frémont's actions are counterproductive.
Frémont leaves California in March but will return to California and take control of the California Battalion following the outbreak of the Bear Flag Revolt in Sonoma.
