The city of Morris is the county seat of Grundy County, Illinois, United States and part of southwest Chicagoland. The population was 13,636 at the 2010 census, making it the largest community in Grundy County.While not technically within the corporate limits of the city, Dresden Nuclear Power Plant, which provides a substantial portion of the electricity supply for the Chicago metropolitan area, has a Morris mailing address. Included among the Dresden plant's reactors is the first commercial nuclear reactor, housed in a spherical concrete and steel shell; it has since been decommissioned, and two more modern reactors now generate its electricity. Also nearby is the Morris Operation—the only de facto high-level radioactive waste storage site in the United States.