The Marshall County Highway Department is responsible for the survey, design, construction, inspection, and maintenance of all roads and bridges under its jurisdiction.

There are five classes of roadways in Marshall County: Trunk Highways, County State Aid Highways, County Roads, Township Roads, and City Streets. Roads under county jurisdiction are County State Aid Highways and County Roads.

County State Aid Highways are identified by having a road number of less than 100 and are established as a grid system throughout the county. The county receives a portion of the gas tax and vehicle registration tax to help maintain and reconstruct these roads. Marshall County has a total of 640 miles of County State Aid Highways.

County Roads are identified by having a number greater than 99 and form an important link between Township Roads and County State Aid Highways. Marshall County maintains 190 miles of County Roads and the only funding source is the local property tax levy.

In addition to the 830 miles of roads under county jurisdiction, the highway department does the annual bridge safety inspection and must maintain, repair, and replace 278 bridges. Any structure with a span of 10 feet or greater is defined as a bridge. Several funds such as Federal and State funds, Town Bridge funds, State Bridge Bond funds, and Local Property Tax Levies are available for bridge replacement or rehabilitation.