Macomb is a city located in McDonough County, Illinois founded in 1830. It is situated in western Illinois southwest of Galesburg at 40°27'38" North, 90°40'27" West (40.460501, -90.674048). As of 2000, the city had a population of 21,659. It is the county seat of McDonough County. According to the United States Census Bureau, the city has a total area of 10.2 square miles, of which, 9.9 square miles (25.5 km²) of it is land and 0.4 square miles (1.0 km²) of it is water. The total area is 3.90% water; the East Fork La Moine River flows past the northern part of the city. Macomb is the home of Western Illinois University.