Thornapple River

Thornapple River
Enhanced USGS Satellite Image, Thornapple River drainage basin.
Native name	Tomba-Signe (or "river with the forked stream")
Country	United States
State	Michigan
Counties	Drainage basin covers portions of Barry, Eaton, Ionia, and Kent Counties in Central Michigan
Basin features
Main source	S of Boody Lake, Eaton Township, Eaton County, Michigan
River mouth	Grand River, Ada Township, Kent County, Michigan 617 ft (188 m)
Physical characteristics
Length	88 mi (142 km)
Discharge	Average rate: 1,000–1,500 cu ft/s (28–42 m3/s) at mouth

The Thornapple River (GNIS ID #1075813) is an 88.1-mile-long (141.8 km)tributary of Michigan's longest river, the Grand River. The Thornapple rises in Eaton County, Michigan and drains a primarily rural farming area in Central Michigan. It joins the Grand in Ada, Michigan, 10 miles (16 km) east of Grand Rapids.

The Thornapple, a major Grand River tributary, is about 88 miles (142 km) long. Its headwaters are located about 7 miles (11 km) east of Charlotte, Michigan in Eaton County's Eaton township (only 7 miles (11 km) west of the Grand River at Eaton Rapids). It flows generally west and north through Eaton and Barry counties, before entering the Grand in Kent County. The Grand ultimately flows into Lake Michigan at Grand Haven, approximately 70 miles (110 km) down stream. The Thornapple is described as "An easygoing stream that meanders through low southwest Michigan woodlands." The Thornapple itself has a major tributary in the Coldwater River. The Thornapple is the only major left tributary of the Grand River.

The major rivers and streams within the Grand River watershed were formed during the epoch and the subsequent advance/retreat glaciation cycle, terminating about 6–8000 years ago. Prior to European settlement, the Thornapple drainage basin had mixed hardwood/conifer forest and barrens. and was home to the Ottawa and Potawatomi Native Americans. who called it the Tomba-Signe (or "river with the forked stream")