Sac City is a city in and the county seat of Sac County, Iowa, United States, located in the rolling hills along the valley of the North Raccoon River, in one of America's prime agricultural regions. U.S. Route 20 bisects the city, forming its Main Street, and the city is one of 45 designated Main Street Iowa communities through the Main Street Iowa development program. The population was 2,220 in the 2010 census, a decline from the 2,368 population in the 2000 census.