One of the oldest, preserved buildings in Northern California, Petaluma Adobe, is located in Petaluma Adobe State Historic Park. The park was the primary location of Ranch Petaluma and a working ranch of over 60,000 acres from 1834 until 1846. The adobe ranch structure, built through the tireless efforts of Mariano Guadalupe Vallejo was the hub of activity. It is estimated that about 85% of the present walls and 20% of the woodwork is original. Hundreds of Indian laborers lived on the ranch and worked at the trades they had learned at Sonoma Mission. They tended herds of horses, sheep, and cattle, and planted and tended crops of wheat, barley, and corn, which were harvested and stored in the adobe. A trip to the Park will take visitors back in time to the largest privately owned adobe building of the 1830's and 40's. Guests can roam through the vast expanse of the structure and envision what life must have been like within the walls of the adobe. The building is registered national history landmark, and is listed as state historical Landmark number l8. Many of the rooms have been decorated with genuine, rancho period furniture and equipment. Visitors see exhibits and visualize some of the activities that once took place. Guided tours for schools and other groups can be arranged.