The Iroquois River enters the county from Indiana and flows westward along the south side of the village of Iroquois, then along the north side of the city of Watseka, whereupon it veers to the north and joins the larger Kankakee River near the city of Kankakee in the county of the same name; the Kankakee River then flows into the Illinois River further to the northwest in Will County. Sugar Creek, further to the south, also flows from the east to the west, entering from Indiana east of Stockland; it passes through the south edge of Milford, is joined by Mud Creek coming up from the south, and winds to the north past the village of Woodland and meets the Iroquois River near Watseka.