Cyrus Alexander (1805–1872) was an early settler of Sonoma County, California.Cyrus Alexander was born in Pennsylvania, and his family soon moved to Illinois. In 1831, Alexander was in the Rocky Mountains trapping for the Sublette fur company. He arrived in San Diego in 1833, where he worked for Captain Henry D. Fitch and became a Mexican citizen.In 1840, Alexander embarked on a scouting expedition for a suitable tract of land for a cattle ranch for Fitch and came to the Russian River Valley.