The Main Building of the fort is a two story adobe structure built between 1841 and 1843. This building is the only original surviving structure at the reconstructed Sutter's Fort State Historic Park. It was in here on January 28, 1848 that James Marshall met privately with Sutter in order to show Sutter the gold that Marshall had found during the construction of Sutter's sawmill along the American River only four days earlier. Sutter built the original fort with walls 2.5 feet thick and 15 to 18 feet high.