Reference

It didn't take long before more than 150 miners poured into the area. As was often the case, a town quickly sprung up to support the mining operation. At its peak in 1853, Mormon Island had over 2,500 residents, four hotels, three dry-goods stores, five general merchandise stores, an express office, numerous small shops and seven saloons.

Early in March 1848, W. Sidney, S. Willis, and Wilford Hudson, members of the Mormon Battalion, set out from Sutter's Fort to hunt deer. Stopping on the south fork of the American River, they found gold. They told their story on returning to the fort, and soon about 150 Mormons and other miners flocked to the site, which was named Mormon Island.

Mormon Island was a natural stopping point between Sutter's Fort and Coloma; by 1850, two stage lines operated. The first ran from Sacramento to Coloma, stopping at Mormon Island. The other ran from Sacramento to Mormon Island and back. The town had become one of the main communities of the Mother Lode. In 1851, a post office was established.