St. Helena is a city in Napa County, California, United States. It is part of the northern San Francisco Bay Area. The population was 5,814 at the 2010 census. Ellen White, co-founder of the Seventh-day Adventist Church, had a home called "Elmshaven" near St. Helena, beginning in 1900. She died there in 1915 and the site is now a National Historic Landmark. The St. Helena AVA is in the region.