Marysville is the county seat of Yuba County, California, United States. The population was 12,072 at the 2010 census, down from 12,268 at the 2000 census. It is included in the Yuba City Metropolitan Statistical Area, often referred to as the Yuba-Sutter Area after the two counties, Yuba and Sutter. The metropolitan statistical area is part of the Greater Sacramento area.
In 1842, John Sutter leased part of his Rancho New Helvetia land to Theodore Cordua, a native of Mecklenburg in Germany, who raised livestock and, in 1843, built a home and trading post he called New Mecklenburg. The trading post and home was situated at what would later become the southern end of 'D' Street, Marysville's main street. In 1844, the Mexican government granted Cordua his own land grant, Rancho Honcut.
In 1848, a former employee of Cordua, Charles Covillaud, discovered riches in the gold fields and bought half of the Cordua ranch. Then, in January 1849, Michael C. Nye and William Foster Nye, brothers-in-law to Covillaud's wife, Mary Murphy, bought the other half of the Cordua ranch. They later sold their interest to Covillaud. In October of the same year, Covillaud sold most of the ranch to Jose Ramirez, John Sampson, and Theodore Sicard. In the days of the Gold Rush, the ranch was a stopping point for riverboats from Sacramento and San Francisco that carried miners on their way to the digging grounds. A sign on the roadside as one enters Marysville still carries the slogan: "Gateway to The Gold Fields."