Kaskaskia River an alternative name for the Kaskaskia that persists in place names along the river, including Okawville, and in a major tributary, the West Okaw River. The Kaskaskia rises in east central Illinois in several farm ditches along the west side of Champaign. The headwaters of the river is just north of Interstate 74, where it is marked with a sign. The river flows south across rural Champaign and Douglas counties, then southwest across southern Illinois, past Vandalia. It joins the Mississippi from the north approximately northwest of Chester and south-southeast of St. Louis, Missouri. The watershed of the river encompasses
Big Thompson River tributary flows east, through the town of Glen Haven, where it merges with the Big Thompson River in the town of Drake, in the Big Thompson Canyon. From Lake Estes, the river descends 1/2 mile (800 m) in elevation through the mountains in the spectacular 25 mi (40 km) Big Thompson Canyon, emerging from the foothills west of Loveland. It flows eastward, south of Loveland across the plains into Weld County and joins the South Platte approximately 5 mi (8 km) south of Greeley. It receives the Little Thompson River approximately four mi (6 km) upstream from its mouth. Water