The Willow River is a tributary of the Mississippi River

Mississippi River

The Mississippi River is the largest river system in North America. Flowing entirely in the United States, this river rises in western Minnesota and meanders slowly southwards for to the Mississippi River Delta at the Gulf of Mexico. With its many tributaries, the Mississippi's watershed drains...

, approximately 45 mi (72 km) long, in northern Minnesota

Minnesota

Minnesota is a U.S. state located in the Midwestern United States. The twelfth largest state of the U.S., it is the twenty-first most populous, with 5.3 million residents. Minnesota was carved out of the eastern half of the Minnesota Territory and admitted to the Union as the thirty-second state...

 in the United States

United States

The United States of America is a federal constitutional republic comprising fifty states and a federal district...

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It rises in Big Rice Lake, in the Chippewa National Forest

Chippewa National Forest

Chippewa National Forest is a National Forest located in northcentral Minnesota, United States, in the counties of Itasca, Cass, and Beltrami. Forest headquarters are located in Cass Lake, Minnesota. There are local ranger district offices in Blackduck, Deer River, and Walker.-History and...

 in southeastern Cass County

Cass County, Minnesota

Cass County is a county located in the U.S. state of Minnesota. As of 2010, the population was 28,567. Its county seat is Walker. A portion of the Leech Lake Indian Reservation is in the county.-Geography:...

. It flows ESE to Haypoint, then ENE, then turns southwest, flowing around the eastern end of the Cuyuna Iron Range. It joins the Mississippi in Aitkin County

Aitkin County, Minnesota

Aitkin County is a county located in the U.S. state of Minnesota. As of 2010, the population is 16,202. Its county seat is Aitkin. A portion of the Mille Lacs Indian Reservation is in the county.-History:...

, approximately 12 mi (19 km) northwest of Aitkin

Aitkin, Minnesota

As of the census of 2000, there were 1,984 people, 892 households, and 434 families residing in the city. The population density was 1,150.3 people per square mile . There were 969 housing units at an average density of 561.8 per square mile...

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