National Register of Historic Places in Sonoma County
Sonoma Plaza Historic District is comprised of 80 acres containing 28 buildings and two objects of historic significance.
The National Register Statement of Significance reads:
Established June 1835 to check possible Russian expansion from Fort Ross and to control the Indians, Sonoma Pueblo was the chief military base of the Mexican Government in Alta California; Mission San Francisco Solano de Sonoma, founded 1823, is the last of the 21 California missions. On June 14, 1846, the raising of the Bear Flag in the Plaza marked the beginning of the American revolt against Mexican rule.
The eight-acre plaza itself was laid out by General Mariano Vallejo in 1835 as a parade ground for the Mexican soldiers stationed at the Sonoma Presidio. It is the largest central plaza in California, and as the site of the Bear Flag Revolt, it can reasonably claim to be the birthplace of modern California.
The plaza contains only two buildings, the Spanish Colonial Revival City Hall and the Classical Revival Carnegie Library. The San Francisco architect A.C. Lutgens designed both buildings.