One of Californiaβs most iconic landmarks, Rancho Petaluma Adobe is the largest privately built adobe structure in the U.S. and served as the headquarters of General Mariano Guadalupe Vallejoβs vast 67,000βacre ranch in the 1830s. Built in the Monterey Colonial style with thick adobe walls, handβhewn redwood timbers, and wide covered verandas, the twoβstory complex once housed workshops, storerooms, and living quarters for Vallejoβs family and ranch workers. Today, visitors can tour the restored adobe, view authentic furniture and exhibits that bring to life Californiaβs rancho era, and enjoy shaded picnic areas set against sweeping oakβstudded hills.