Sac City is a city in and the county seat of Sac County, Iowa, United States, located just southwest of the eastern intersection of U.S. Routes 20 and 71 in the rolling hills along the valley of the North Raccoon River. The city is one of 45 designated Main Street Iowa communities through the Main Street Iowa development program. The population was 2,063 in the 2020 census, a decline from the population of 2,368 in 2000.