The first settlement of people in what would become Carroll County was in 1828 on the western shore and bluffs overlooking the Mississippi River. Settling on land now occupied by the village of Savanna, the territory became a prime shipping stopover for pioneers buying and trading commodities and necessities, most notably lumber. In the subsequent years more people arrived and more villages sprouted, though a decade would pass before the county was formally recognized and Savanna was awarded the distinction of county seat. It maintained this honor until 1843 when a vote moved the county offices and records ten miles west to Mount Carroll. So named for being built on a hill and honoring Charles Carroll (1737-1832), a native of Annapolis, Maryland, and the last surviving member of those who signed the Declaration of Independence, Mount Carroll had been organized two years before it became the new county seat with the creation of the Mt. Carroll Mill Company and a handful of buildings on the sparse prairie.

With strong commerce, the fledging community began an increase in population and by 1853 the town numbered 800 citizens, including children that required schooling. As a result two women from New York, Miss Cinderella Gregory and Miss Frances Ann Wood, traveled by horse-drawn carriage to establish the Mount Carroll Seminary in the town's Presbyterian Church. The school's education program was ahead of its time - admitting prospective men and women students on the basis of their capability, rather than on their background - and seventy-five students enrolled its first year of operation.

Of its first two teachers, Frances Wood would be associated with the school the longest, presiding over all facets of the institution in its developing years, and eventually giving the college its name, once she married Henry Shimer, a professor and prominent Mount Carroll physician. With Wood's guidance - and the rejection of male students due to a shortage of residential areas - the seminary became a noted, and rare, midwestern woman's school, focusing on intellectual and spiritual development.

Becoming the Francis Shimer School of the University of Chicago in 1896, both the student body and campus ground grew slowly over the next decade, its earliest and most notable setback being a fire that destroyed all the school's historic buildings. Under the leadership of Dean William McKee, ten new buildings quickly were built to supplement the only two that survived. During the 1940's and 1950's the college returned to its coeducational status, expanded the course of study to four years of college work, and adopted the University of Chicago's Hutchins Plan, an integrated curriculum of primary sources and discussion classes.

During the 1960 and 70s the college was affiliated with the Episcopal Church and reached its all-time high enrollment of 550 students, though students and money declined steadily over the next decade. Besieged with debt and becoming increasingly isolated, various attempts were made to keep the college afloat. The 14-acre Mount Carroll campus was eventually purchased at bankruptcy auction in 1979 by the Campbell Center for Historic Preservation Studies, placed on the National Register of Historic Sites the following year, and today has been in continuous use by an educational institution for over 150 years. Shimer College moved to Waukegan shortly thereafter and, in 2006, again moved to Chicago, where they operate a student body between 120 and 150 students.