Gabriel Moraga (1767-1785) was a lieutenant in the Spanish Army and the European to see the Sutter Buttes, which he called Los Picachos ("The Peaks"). He explored the Sacramento and San Joaquin Valleys in 1806-1808, leading the Spanish army through the valley and displacing local Native American groups such as the Nisenan, who lived in the area that is now Yuba and Sutter Counties. Many of the names he invented for the places he saw are still used today. For example, he named Sacramento ("blessed sacrament") and San Joaquin ("Saint Joaquim").
Surviving documents written by Moraga and his soldiers describe their amazement at the huge numbers of animals living in the valley. Everywhere they went, they were surrounded by antelope, deer, elk, grizzly bears, raccoons, squirrels, and other native animals. No invasive weeds or invasive animals had arrived here yet, and California's now-famous "golden hills" were not yet golden at all. Most of the dominant native grass species throughout the state were perennials that turned a dull blue-green when they went dormant over the dry summer months, rather than the yellow-brown of the invasive alien annual grasses that are now dominant throughout most of California.