The last of the California Missions, Mission San Francisco Solano was founded in 1823 and is now a California Historic Landmark and an important part of Sonoma State Historic Park. The church that now stands on the mission grounds is a restored version of the church built in 1840; the last major restoration took place in 1943. One wing of the building has now been converted into a museum displaying mission paintings and other important artifacts, and the former soldiers' barracks across the street from the mission now house a gift shop and a second, smaller museum.

Mission San Francisco Solano was founded on July 4, 1823, and named for Francis Solanus, a missionary to the Indians of Peru born in Montilla, Spain, known as the "Wonder Worker of the New World." Originally planned as an asistencia to Mission San Rafael Arcángel, it is the northernmost Alta California Franciscan mission. The mission is located in present-day Sonoma, California, at 114 East Spain Street. The mission was built by the Mexican authorities as a barrier to Russia's attempts to extend control to the federal territory of Alta California. During the years the Mission was active, General Mariano Vallejo resided in town. He was tasked with monitoring the activities of Russia at their nearby settlement of Fort Ross, and with establishing peaceful relations with the Native Americans of the region. Vallejo helped to build the town of Sonoma and even paid for the rebuilding of the small Mission chapel. There were always soldiers and settlers in the town of Sonoma during the Mexican period. The Franciscan Fathers grew grapes and produced sacramental wine from the first vineyard in the Sonoma Valley, which was first planted in 1825. By 1834, Vallejo had the Rancho Petaluma Adobe built a few miles to the west, which became a large agricultural body operation to support the Spanish military here.

Mission San Francisco Solano was the 21st, last, and northernmost mission in Alta California. It was the only mission built in Alta California after Mexico gained independence from Spain. The difficulty of its beginning demonstrates the confusion resulting from that change in governance. The California Governor wanted a robust Mexican presence north of the San Francisco Bay to keep the Russians who had established Fort Ross on the Pacific coast from moving further inland. A young Franciscan friar from Mission San Francisco de Asis wanted to move to a location with a better climate and access to a larger number of potential converts.The experiment was successful, given its short eleven year life, but was smaller in number of converts and with lower productivity and diversity of industries than the older California missions.The mission building is now part of the Sonoma State Historic Park and is located in the city of Sonoma, California.