Iowa County Map: All 99 Counties

In 1851, the Third Iowa General Assembly established 49 new counties across the prairie, aiming for uniform 24-mile-by-24-mile squares (576 square miles). This blueprint created 100 counties initially.

However, in northern Iowa, Bancroft County had insufficient dry land due to extensive glacial marshlands. In 1857, the Iowa Legislature dissolved Bancroft County and merged its 16 townships into neighboring Kossuth County, giving Kossuth its double-height rectangular shape and making it Iowa’s largest county (973 square miles).

Lee County in southeast Iowa retained two county seats: Fort Madison in the north and Keokuk in the south, established in 1848 to resolve intense commercial rivalries between upper and lower Mississippi River steamboat ports.

Under the direction of a mandatory County Engineer (a licensed professional engineer appointed by the Board of Supervisors), Iowa counties maintain over 89,000 miles of secondary roads and over 18,000 bridges.

Additionally, Iowa Code Chapter 468 grants county supervisors legal authority to act as trustees for Agricultural Drainage Districts. In glaciated northern Iowa (the Des Moines Lobe), subsurface ceramic tile networks and ditch canals constructed by county drainage districts converted millions of acres of prairie wetlands into the most productive corn and soybean soil on Earth.