More than twenty-five men petitioned the York County Court to establish Carroll Township in 1831 by annexing an eastern section of Franklin Township and a western section of Monaghan Township.
Carroll Township is bounded by Cumberland County on the north, Monaghan Township on the east, Warrington Township on the south and Franklin Township on the west. It surrounds the Borough of Dillsburg.
In 1880, the population was 1,338. By the year 2000, it was 4,715 and as of 2018 the population is reported to be 6,508.
The Harrisburg and Potomac Railroad crossed the northern edge of the county along the Yellow Breeches Creek and the Mechanicsburg and Dillsburg Railroad spur connected Dillsburg at the north end of the Borough.
In 1847, west of Ore Bank Road on his farm, Abraham Mumper discovered magnetite iron ore about three feet below the ground’s surface. This changed a primarily agricultural community into a mining area for about sixty years. As recent as the mid 1940’s, a U.S. Government survey determined significant deposits of iron ore still exist in the area. More than 120,000 tons of ore have been mined from about a dozen mining operations.
In 1952, the Northern (Joint Area) School District was formed, and a new high school was built in Carroll Township to accommodate the growing area’s educational needs.