Stillwater River (Ohio)

Stillwater River
Stillwater River flows under Interstate 70 near Dayton, Ohio
Physical characteristics
Source 
  locationNear Union City, Ohio
  elevation~ 1,050 ft (320 m)
Mouth 
  location
Great Miami River in Dayton
  elevation
~ 750 ft (230 m)
Length69 miles (111 km)
Basin size682 sq mi (1,770 km2)
Discharge 
  locationEnglewood
  average632.2 cu ft/s (17.90 m3/s), USGS water years 1926-2019

The Stillwater River is a 69.3-mile-long (111.5 km) tributary of the Great Miami River in western Ohio in the United States. Via the Great Miami and Ohio rivers, it is part of the Mississippi River watershed.

It rises near the Indiana state line, in western Darke County, approximately 10 miles (16 km) northwest of Greenville. It flows east-southeast and is joined by Greenville Creek in Covington, approximately 5 miles (8 km) west of Piqua. It flows south past Covington and Englewood, where it is dammed for flood control, then southeast to join the Great Miami River in Dayton.

Stillwater River was so named on account of its relatively slow current. The Stillwater River was one of the Great Miami River tributaries that flooded during the Great Dayton Flood of 1913, resulting in the creation of the Miami Conservancy District.