Named for the abundant ash trees lining the San Joaquin River, Fresno was founded in 1872 as a railway station of the Central Pacific Railroad before it was incorporated in 1885. It covers about 112 square miles (290 km 2) and had a population of 542,107 in 2020, making it the fifth-most populous city in California, the most populous inland city in California, and the 34th-most populous city in the nation. It is the county seat of Fresno County and the largest city in the greater Central Valley region.