Sussex County is a county located in the southern part of the US state of Delaware. As of 2010 the population was 197,145, an increase of 25.9% over the previous decade. The county seat is Georgetown. The Seaford Micropolitan Statistical Area, which is the largest micropolitan area in the United States, includes all of Sussex County. Sussex County is Delaware's largest county by land area, with 938 square miles (2,429 km).