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.

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.

According to the 2021 census gazetteer files, Mount Carroll has a total area of 2 square miles (5.18 km2), all land.

Due to its elevation and northwesterly location, Mount Carroll is subject to unusually cold winter weather.

Mount Carroll enjoys a remarkable concentration of historically and architecturally significant structures.

The Timber Lake Playhouse, the oldest semiprofessional summer stock theater company in Illinois, is located 4 miles (6 km) southeast of Mount Carroll.

The Mount Carroll post office contains an oil on canvas mural, Rural Scene - Wakarusa Valley, painted by Irene Bianucci in 1941.