Glenn is one of the 58 counties in the state of California. It was created in 1891 from parts of Colusa county. As of the 2010 census the population was 28,122, up from 26,453 in 2000. The county seat is Willows, and the largest city is Orland.
It covers 1,327.16 square miles (3,437.3 km2), of which 1,314.79 square miles (3,405.3 km2) is land. It is bordered by Tehama County to the north, Butte County to the east, Colusa County to the south, Lake County to the southwest and Mendocino County to the west.