Rohnert Park is a city in Sonoma County, California, United States, located approximately 50 miles (80km) north of San Francisco. The population at the 2010 United States Census was 40,971. It is an early planned city and is the sister city of Hashimoto in Japan. Sonoma State University, part of the California State University system, is located nearby. According to the United States Census Bureau, Rohnert Park has a total area of 7.0 square miles (18km2), 99.93% of it land and 0.07% of it water.