Rock Island County

Rock Island County is an administrative division in western Illinois bordered by the Mississippi River and containing the cities of Rock Island and Moline. The county spans rolling terrain with river bottomlands and supports several smaller communities across its landscape.

The county was established in 1831 when it was separated from Jo Daviess County and took its name from an island in the Mississippi River that became known as Arsenal Island. Military manufacturing grew into a major economic force during the 1800s and shaped regional development.

The military arsenal on the island shaped how local communities developed and provided steady work for generations of families. This industrial heritage remains visible in how people use the waterfront and in the character of the nearby towns.

Three interstate highways cross the area, making it easy to reach from other parts of the region, and offering connections to major cities in the Midwest. The Mississippi River serves as a natural landmark that helps with orientation when exploring the county.

The county has maintained a consistent Democratic voting pattern since the 1930s, a notable shift from its earlier Republican leanings that set it apart from many other regions of the state. This political continuity offers insight into how economic and industrial changes influenced local voting habits over time.

Location: Illinois

Inception: 1831

Capital city: Rock Island

Shares border with: Clinton County, Mercer County, Muscatine County, Henry County, Whiteside County, Scott County, Louisa County

Website: http://co.rock-island.il.us

GPS coordinates: 41.47000,-90.57000

Latest update: December 20, 2025 15:53