Mount Carroll is a city in Carroll County, Illinois, United States. It is the Carroll County seat. The population was 1479 at the 2020 census. Due to its elevation and northwesterly location, Mount Carroll is subject to unusually cold winter weather. From 1930 to 1999, Mount Carroll held the record for the lowest temperature ever recorded in Illinois, , recorded on January 22, 1930. The record was beaten by Congerville in 1999, by one degree Fahrenheit. 20 years later, on January 31, 2019 during an extreme cold snap, Mount Carroll regained the title of coldest city in Illinois when a new Illinois state record low temperature of was officially recorded. History Mount Carroll began life as a mill town around 1841. In 1843, a referendum moved the county seat from nearby Savanna to Mount Carroll. The town was incorporated in 1855 and became a city in 1867; the first mayor was Nathaniel Halderman, a prominent local businessman and co-founder of the mill. Shimer College was established in Mt. Carroll in 1853, but mounting debts forced a move to Waukegan in 1979 and subsequently to Chicago in 2006. The campus now is home to several organizations, most notably the Campbell Center for Historic Preservation Studies. Geography Mount Carroll is located slightly northwest of the center of Carroll County at (42.095473, -89.977042). U.S. Route 52 passes through the southern part of the city, leading east to Lanark and west to Savanna on the Mississippi River. According to the 2021 census gazetteer files, Mount Carroll has a total area of , all land. Climate Mt. Carroll has a humid continental climate (Köppen climate classification: Dfa), with cold winters, hot summers, and four seasons. Annual precipitation is about 40 inches. Major highways U.S. Route 52 and Illinois Route 64 (concurrent with US 52), east towards Lanark, west towards Savanna and the Mississippi River. Illinois Route 40, south towards Chadwick, Milledgeville and Sterling-Rock Falls. Illinois Route 78, north towards Stockton, south towards Morrison. Arts and culture Mount Carroll enjoys a remarkable concentration of historically and architecturally significant structures. The bulk of the town's downtown and older residential area are included in the Mount Carroll Historic District, which encompasses and was entered into the National Register of Historic Places in 1980. Mount Carroll is also home to the Campbell Center for Historic Preservation Studies, located on the historic former Shimer College campus near the south edge