There are 8 US Post Offices in Glenn County serving a total of 29,238 residents equating to 3,655 residents per post office. It's estimated that approximately 46,667 packages are handled across the 8 county post offices annually. Glenn County is a county in the U.S. state of California. As of the 2010 census, the population was 28,122. The county seat is Willows. It is located in the California Central Valley."