Livermore is a city in Alameda County, California. With a 2020 population of 87,955, Livermore is the most populous city in the Tri-Valley. It is located on the eastern edge of California's San Francisco …Livermore is a city in Alameda County, California. With a 2020 population of 87,955, Livermore is the most populous city in the Tri-Valley. It is located on the eastern edge of California's San Francisco Bay Area. The current mayor is John Marchand.