Sonoma, the last of the mission towns to be established, was fortified in the 1830s to protect Mexico's frontier from encroaching Russian settlements to the north. Picnic or dine on the historic Sonoma Plaza, then visit the former Mexican barracks and the 1823 Mission San Francisco Solano de Sonoma.
West of Sonoma, in Petaluma, board a steamboat for a ride on the Petaluma River. Then visit Petaluma Adobe State Historic Park, the remains of a once-vast rancho.
Don't miss the 800-acre Jack London State Historic Park north of Sonoma near forested Glen Ellen. Survey the ruins of London's dream home, which burned down just before he and his wife moved in. In Santa Rosa, tour the Luther Burbank Home and Gardens and the Church Built from One Tree, now a museum.
North of Santa Rosa, you can canoe in the Russian River past lovely vineyards. More than 50 wineries are clustered along the river's banks in the Russian River Valley. Hike the nature trail in Armstrong Redwoods State Reserve near Guerneville. Monte Rio features riverfront beaches, romantic inns, and interesting shops and restaurants. North of picturesque Jenner- by-the-Sea stands Fort Ross State Historic Park, established as a Russian outpost in 1812. Farther north on the coast is Kruse Rhododendron State Reserve, where flowers bloom from April to June.