Casey Creek (Illinois) and Atchison Creek. Gun Creek, which enters Rend Lake on the east side, might also be considered a Casey Creek tributary. Casey Creek (Illinois) Casey Creek is a major tributary of the Big Muddy River in Illinois, United States. It is about long, measured from the junction of its arm of Rend Lake with the arm formed by the Big Muddy River. Casey Creek is shown on federal maps as Casey Fork, following a 1967 decision by the U.S. Board on Geographic Names. It is named for Zadok Casey, a congressman from Illinois in the early 19th century. Casey Creek
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