Prior to European colonization, the land that now makes up Carroll County was inhabited by Native Americans for thousands of years.

Numerous Native American archaeological sites and archeological artifacts have been located across the county.

Native Americans used the land for permanent settlements, seasonal visits and journeys, and as hunting grounds.

[3] At the time of European colonization, the Susquehannock and the Lenape were the predominant indigenous nations in the area.

What is now the city of Manchester was inhabited by the Susquehannock nation until around 1750 and was the location of the intersection of two important Native American trails.

[9] Maryland Route 26 (Liberty Road) was built over top what was originally a Native American trail.

This trail passed through the Freedom area of southern Carroll County and was used by Native Americans to travel from the Blue Ridge Mountains to the Chesapeake Bay.

The trail was transformed into a road and renamed "Liberty" by an act of the Maryland General Assembly in the early 1800s.

Due to the Six Nations land cessions, the Tuscarora were expelled westward across the South Mountain of the Cumberland Valley.

[16] During the American Civil War, the population of Carroll County was sharply divided between supporters of the Union and the Confederacy.

[18] The KKK held rallies and handed out leaflets on Main Street in Westminster and in Manchester until the late 1980s.

[23] In 2018, the Carroll County Public Schools announced that Confederate flags and Nazi swastikas would be banned from Carroll County schools, along with Ku Klux Klan and Aryan Nation symbolism and other messages that promote hatred or intolerance.

[25] Topographically, Carroll County is located within the Piedmont Plateau region, with characteristic upland terrain of rolling hills and deciduous forest.

The highest point is an unnamed 1,120-foot (340 m) hilltop a half-mile south of the Pennsylvania state line in the northeastern part of the county off Harvey Yingling Road.

The old Baltimore and Ohio (B&O) Old Main Line crosses the southern part of the county from east to west, with former stations in Sykesville and Mount Airy.

The original Western Maryland Railway (WM) main line track runs southeast to northwest through Carrollton, Westminster, New Windsor, and Union Bridge.

The old Baltimore and Hanover Railroad (later acquired by WM) runs further to the east through Hampstead, Millers, and Lineboro.

[34] In terms of ancestry, 33.8% were German, 19.1% were Irish, 14.0% were English, 8.4% were American, 8.2% were Italian, 5.3% were Polish, 2.8% were French and 2.3% were Scottish.

Since World War I ended, the only other Democrat to carry Carroll County has been Franklin D. Roosevelt, who managed to achieve this only during his initial 1932 campaign.

Before World War I Carroll County had considerable Confederate sympathy and hence leaned Democratic,[43] although it did vote twice for William McKinley.

In the 2012 presidential election, 65 percent of the county's vote went for Republican candidate Mitt Romney.

In Maryland's 2014 gubernatorial race, Carroll County voted for Republican Larry Hogan over Democrat Lieutenant Governor Anthony Brown by sixty-six percentage points (82 to 16 percent).

Due to longstanding opposition to mass transit from local residents and politicians, there is no inter-county bus or rail transit linking Carroll County to nearby suburban communities of Baltimore County.

In addition to providing police services, the Sheriff's Office also acts as an agent of the courts: serving warrants, enforcing child support laws, ensuring courthouse security, transporting prisoners, etc.

The police department would handle primary law enforcement duties while the Sheriff's office would continue to act under the arm of the courts.

This move would give the Commissioners power to appoint or fire the chief of police instead of having a popularly elected Sheriff being in charge of all law enforcement.