The mountain has five peaks, arranged in a rough "M" shape. Its highest point, North Peak, is in Sonoma County. The second-tallest, immediately east of the main summit, is the highest point in Napa County.[5] The headwaters of the Napa River arise on the southeast slope of Mount Saint Helena.[6][7]
Mount Saint Helena, originally named Kanamota ("Human Mountain") by the Wappo, and later Mount Mayacamas by Spanish colonists, was renamed by a Russian survey party who ascended the peak in 1841. They left a copper plate on the summit inscribed with the date of their visit and the name of Princess Helena de Gagarin, wife of Alexander G. Rotchev, the commanding officer of Fort Ross.[8][9]