Theodore Sicard was a sailor, gold miner, and merchant. Sicard Street in Marysville and Sicard Flat are named for him. His name was sometimes spelled Chicard.

Born in France, he came to California in 1835. From 1842 to 1843, he worked for John Sutter as the manager of Hock Farm. He successfully petitioned the Mexican government to obtain a land grant of four Spanish leagues, extending ten miles along the south bank of Bear River, from opposite the mouth of Dry Creek (the southernmost of the two Yuba County creeks called Dry Creek) to about half a mile above Johnson's Crossing. He moved to Marysville in 1848. In 1849, he purchased part of Theodor Cordua's Marysville ranch from Charles Julian Covillaud.