Carroll County is a county located in the U.S. state of Maryland. Carroll County is included in the Baltimore-Columbia-Towson, MD Metropolitan Statistical Area, which is also included in the Washington-Baltimore-Arlington, DC-MD-VA-WV-PA Combined Statistical Area. While predominantly rural, the county has become increasingly suburban in recent years.


Carroll County is bordered on the north by the Mason–Dixon line with Pennsylvania, and on the south by Howard County across the South Branch of the Patapsco River. About half of the eastern border, with Baltimore County, is formed by the North Branch of the Patapsco River and by Liberty Reservoir, though the northern half near Manchester and Hampstead is a land border. Carroll County is bordered on the west by Frederick County, across the Monocacy River and Sam’s Creek. Other major streams in the county include Big Pipe Creek, Little Pipe Creek, and Double Pipe Creek, Bear Branch, and the headwaters of the Gunpowder Falls. The Piney Run Reservoir is in the southern part of the county. Topographically, Carroll County is located within the Piedmont Plateau region, with characteristic upland terrain of rolling hills and deciduous forest. The most prominent relief is Parr’s Ridge, which bisects the county from southwest to northeast. The highest point is in the northeastern part of the county on Dug Hill along Deep Run Road.


The Carroll County Public Schools School system is the ninth largest school district in the state of Maryland. McDaniel College, a small private liberal arts college, is located in Westminster.