When the first Europeans arrived, the area was near the northeast corner of the Coast Miwok territory, with Southern Pomo to the northwest, Wappo to the northeast, Suisunes and Patwin peoples to the east.
Mission San Francisco Solano was the predecessor of the Pueblo of Sonoma. The Mission, established in 1823 by Father José Altimira of the Franciscan Order was the 21st, last and northernmost mission built in Alta California. It was the only mission built in Alta California after Mexico gained independence from the Spanish Empire. In 1833 the Mexican Congress decided to close all of the missions in Alta California. The Spanish missionaries were to be replaced by parish priests. The commander of the Company of the National Presidio at San Francisco (Compania de Presidio Nacional de San Francisco), Lieutenant Mariano Guadalupe Vallejo was appointed administrator (comisionado) to oversee the closing of Mission San Francisco Solano. Governor José Figueroa’s naming of Lieutenant Vallejo as the administrator to secularize the Mission was part of a larger plan.
Governor Figueroa had received instructions from the National Government to establish a strong presence in the region north of the San Francisco Bay to protect the area from encroachments of foreigners. An immediate concern was the further eastward movement of the Russian America Company from their settlements at Fort Ross and Bodega Bay on the California coast.
Figueroa’s next step in implementing his instructions was to name Lieutenant Vallejo as Military Commander of the Northern Frontier and to order the soldiers, arms and materiel at the Presidio of San Francisco moved to the site of the recently secularized Mission San Francisco Solano. The Sonoma Barracks were built to house the soldiers. Until the building was habitable, the troops were housed in the buildings of the old Mission. In 1834, George C. Yount, the first Euro-American permanent settler in the Napa Valley, was employed as a carpenter by General Vallejo.
The Governor granted Lieutenant Vallejo the initial lands (approximately 44,000 acres (178 km2)) of Rancho Petaluma immediately west of Sonoma. Vallejo was also named Director of Colonization which meant that he could initiate land grants for other colonists (subject to the approval of the governor) and the diputación (Alta California’s legislature).
Vallejo had also been instructed by Governor Figueroa to establish a pueblo at the site of the old Mission. In 1835, with the assistance of William A. Richardson, he laid out, in accordance with the Spanish Laws of the Indies, the streets, lots, central plaza and broad main avenue of the new Pueblo de Sonoma.
Although Sonoma had been founded as a pueblo in 1835, it remained under military control, lacking the political structures of municipal self-government of other Alta California pueblos. In 1843, Lieutenant Colonel Vallejo wrote to the Governor recommending that a civil government be organized for Sonoma. A town council (ayuntamiento) was established in 1844 and Jacob P. Leese was named first alcalde, and Cayetano Juarez second alcalde.
Before dawn on Sunday, June 14, 1846, thirty-three Americans, already in rebellion against the Alta California government, arrived in Sonoma. Some of the group had traveled from the camp of U.S. Army Brevet Captain John C. Frémont who had entered California in late 1845 with his exploration and mapping expedition. Others had joined along the way. As the number of immigrants arriving in California had swelled, the Mexican government barred them from buying or renting land and threatened them with expulsion because they had entered without official permission. Mexican officials were concerned about the coming war with the United States coupled with the growing influx of American immigrants into California.
A group of rebellious Americans had departed from Frémont’s camp on June 10 and captured a herd of 170 Mexican government-owned horses being moved by Californio soldiers from San Rafael and Sonoma to Alta California’s Commandante General José Castro in Santa Clara. The insurgents next determined to seize the weapons and materiel stored in the Sonoma Barracks and to deny Sonoma to the Californios as a rallying point north of San Francisco Bay.
Meeting no resistance, they approached Comandante Vallejo’s home and pounded on his door. After a few minutes, Vallejo opened the door dressed in his Mexican Army uniform. Vallejo invited the filibusters’ leaders into his home to negotiate terms. However, when the agreement was presented to those outside they refused to endorse it. Rather than releasing the Mexican officers under parole, they insisted they be held as hostages. William Ide gave an impassioned speech urging the rebels to stay in Sonoma and start a new republic. Referring to the stolen horses Ide ended his oration with “Choose ye this day what you will be! We are robbers, or we must be conquerors!” At that time, Vallejo and his three associates were placed on horseback and taken to Frémont accompanied by eight or nine of the insurgents who did not favor forming a new republic under the circumstances.
The Sonoma Barracks became the headquarters for the remaining twenty-four rebels, who within a few days created their Bear Flag. After the flag was raised Californios called the insurgents Los Osos (The Bears) because of their flag and in derision of their often scruffy appearance. The rebels embraced the expression, and their uprising became known as the Bear Flag Revolt.
There were some small unit skirmishes between the Bears and the Californios but no major confrontations. Hearing reports that Mexican General José Castro was preparing to attack, Frémont left his camp near Sutter’s Fort for Sonoma on June 23. With him were ninety men – his own party plus some trappers and settlers.
On July 5, Frémont called a public meeting and proposed to the Bears that they unite with his party and form a single military unit. He said that he would accept command if they would pledge obedience, proceed honorably, and not violate the chastity of women. A compact was drawn up which all volunteers of the California Battalion signed or made their marks. The next day Frémont, leaving the fifty men of Company B at the Barracks to defend Sonoma, left with the rest of the Battalion for Sutter’s Fort. They took with them two of the captured Mexican field pieces, as well as muskets, a supply of ammunition, blankets, horses, and cattle.
War against Mexico had already been declared by the United States Congress on May 13, 1846. Because of the slow cross-continent communication of the time, no one in California knew that conclusively. Commodore John D. Sloat, commanding the U.S. Navy’s Pacific Squadron, had learned of Frémont’s support for the Bears in Sonoma. Sloat finally concluded on July 6 that he needed to act, “I shall be blamed for doing too little or too much – I prefer the latter.” Early July 7, the United States Navy, captured Monterey, California, and raised the flag of the United States. Sloat had his proclamation read and posted in English and Spanish: “…henceforth California will be a portion of the United States.”
The Bear Flag Revolt and whatever remained of the “California Republic” ceased to exist on July 9 when U.S. Navy Lieutenant Joseph Revere raised the United States flag in front of the Sonoma Barracks and sent a second flag to be raised at Sutter’s Fort.
Until May 26, 1848, when Mexico and the United States ratified the Treaty of Guadalupe Hidalgo, Alta California was officially militarily occupied enemy territory. Until a civilian authority was established the military decided to retain the Mexican administrative and judicial system of prefects for districts and alcaldes for municipalities. This continued even after California became part of the United States because Congress never did organize California as a U. S. territory. California remained a military district so the old Mexican laws, supplemented by pronouncements of the military governors, largely remained in place. California would finally achieve statehood on September 9, 1850, as part of the slavery-focused Compromise of 1850.
Company B of the California Battalion, which had been left in Sonoma for the protection of the town, was soon placed under U.S. Navy command. The American immigrants who comprised Company B eventually returned to their homes. Sonoma’s Alcalde complained to the U.S. Navy about the lack of protection for the town and a detachment of U.S. Marines was assigned to the Sonoma Barracks. In March 1847, the Marines were replaced by Company “C” of what was called Stevenson’s New York Volunteers. The enlistments of the New York Volunteers ended with the war and they were replaced in May 1849, by a 37-man company of U.S. dragoons (Company C, 1st U.S. Dragoons) who moved into the Barracks and established Camp Sonoma. Sonoma was also the headquarters of the Pacific Division of the U.S. Army under Brevet Major General Persifor Smith. Sonoma lost its military population in January 1852, when the troops moved to Benicia and other assignments in California and Oregon. The Army continued to use part of the Barracks as a supply depot until August 1853.
Local businesses prospered with the business brought by the soldiers as well as miners traveling to and from the gold fields. The prosperity and optimism about Sonoma’s future promoted land speculation which was particularly problematic because of the cloudy records regarding land ownership. Vallejo had granted land by virtue of his office as Director of Colonization before the pueblo was organized. Among the traditional duties of Alta California’s alcaldes was the selling of town lots. Political factions backed different Sonoma alcaldes (John H. Nash, supported by American immigrants, and Lilburn Boggs supported by Vallejo and the Californios) made the situation more complex. Some property was sold more than once. A valid land sale depended on proof of the seller’s chain of title. Over thirty years of lawsuits were required before land owners in Sonoma were able to obtain clear titles.
California elected a civilian government (albeit by military order) to organize the state before it was officially formed by the United States Congress in 1850. Sonoma was named the county seat for Sonoma County. About that time the flow of miners had slowed and the U.S. Army was leaving Sonoma. Business in Sonoma moved into a recession in 1851. Surrounding towns such as Petaluma and Santa Rosa were developing and gaining population faster than Sonoma. An 1854 special election moved the county seat and its entailed economic activity to Santa Rosa.