La Moine River Basin
La Moine River is a 125-mile-long (201 km) tributary of the Illinois River in western Illinois that runs directly through Macomb. Its watershed covers approximately 2,000 square miles (5,000 km2), and it is the sixth-largest tributary to the Illinois River. It is part of the watershed of the Mississippi River.
The La Moine or Lamoine River rises in southwestern Warren County and initially flows southwestwardly through southeastern Henderson and northwestern McDonough counties into Hancock County, where it turns to the southeast and flows again through McDonough and then Schuyler counties. In its lower course the river passes the village of Ripley and is used to define a portion of the boundary between Schuyler and Brown counties. It flows into the Illinois River from the northwest, about 4 miles (6 km) southwest of Beardstown.
In its headwaters region the river collects the short South Branch La Moine River, which rises in McDonough County and flows west-southwestwardly into Hancock County, past La Harpe. In Hancock County it collects the East Fork La Moine River, which rises in Warren County and flows south- and southwestwardly through McDonough County, past Macomb.
The United States Board on Geographic Names settled on “La Moine River” as the river’s official name in 1933. According to the Geographic Names Information System, the river has also been known as, Lamoine Creek, Rivière à la Moine or Rivière au Moine (Monk river), Rivière à la Mine (Mine river) and most popularly, Lamoine River and Crooked Creek.