Established in 1830, McDonough County is named for Commodore Thomas McDonough who led a successful battle against the British on Lake Champlain in the War of 1812.
The county has the unusual distinction of forming a perfect square by Mercator map projection. The county seat, Macomb, is in the center of the county, and the courthouse is almost precisely in the center of the county.
The first documented Americans in McDonough County were soldiers from the War of 1812, followed shortly thereafter by teams of surveyors in 1816 that crisscrossed the county in a grid of half mile squares. Most of the county was awarded to veterans of the war as land grants for their services.
Both the surveys and the pattern of lands granted show that the county was not homogenous. The heavily wooded and hilly southwest quarter of the county contained few land grants to the veterans. The county’s first trail was to guide southern Illinois pioneers from Beard’s ferry across the Illinois River to Rock Island and into the mining region of northwestern Illinois.
In 1826 when McDonough County was founded, pioneers began settling in three distinct groupings that became three distinct settlements. When the county was granted self-governing status in late 1830, some of the first items that the commissioners went to work on were the laying out of roads to places of importance. Over the next twenty years, prior to the coming of the railroads, 24 settlements appeared. Almost all of the early settlements disappeared after the railroads came in during the mid-1850s. All the towns that now exist are either on an existing railroad or on a proposed railroad.
According to the 2010 census, McDonough County had a population of 32,612.