The Apple River is a tributary

Tributary

A tributary or affluent is a stream or river that flows into a main stem river or a lake. A tributary does not flow directly into a sea or ocean...

 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...

, about 55 miles (88.5 km) long, in southwestern Wisconsin

Wisconsin

Wisconsin is a U.S. state located in the north-central United States and is part of the Midwest. It is bordered by Minnesota to the west, Iowa to the southwest, Illinois to the south, Lake Michigan to the east, Michigan to the northeast, and Lake Superior to the north. Wisconsin's capital is...

 and northwestern Illinois

Illinois

Illinois is the fifth-most populous state of the United States of America, and is often noted for being a microcosm of the entire country. With Chicago in the northeast, small industrial cities and great agricultural productivity in central and northern Illinois, and natural resources like coal,...

 in the United States

United States

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

. It rises in Lafayette County, Wisconsin

Lafayette County, Wisconsin

Lafayette County is a county located in the U.S. state of Wisconsin. As of 2000, the population was 16,137. Its county seat is Darlington.-Geography:According to the U.S...

, and flows for most of its length in Illinois, through Jo Daviess

Jo Daviess County, Illinois

Jo Daviess County is a county located in the northwest corner of U.S. state of Illinois. According to the 2010 census, it has a population of 22,678, which is an increase of 1.7% from 22,289 in 2000. Its county seat is Galena....

 and Carroll Counties. Along its course it passes through Apple River Canyon State Park

Apple River Canyon State Park

Apple River Canyon State Park is an Illinois state park on 297 acres  in Jo Daviess County, Illinois, USA. The land for the park was purchased by the state in 1932 and preserves the canyon on the Apple River....

 and the town of Hanover

Hanover, Illinois

Hanover is a village in Jo Daviess County, Illinois, along the Apple River. The population was 844 at the 2010 census, up from 836 at the 2000 census- Geography :Hanover is located at ....

. It flows into the Mississippi River about 7 mi (11 km) northwest of Savanna

Savanna, Illinois

Savanna is a city in Carroll County, Illinois, United States. The population was 3,062 at the 2010 census, down from 3,542 at the 2000 census. Savanna is located along the Mississippi River at the mouth of the Plum River. Going from north to south, the second automobile bridge between Iowa and...

.

In Jo Daviess County, it collects two short tributaries known as the West Fork Apple River and South Fork Apple River.

Geology

The river is part of the Driftless Area of Illinois, a region that was bypassed by the last ice age

Wisconsin glaciation

The last glacial period was the most recent glacial period within the current ice age occurring during the last years of the Pleistocene, from approximately 110,000 to 10,000 years ago....

; "the glacial sweep which ironed out hills and filled valleys in other parts of the state left this area unscratched. The Apple River had its original course reversed, it now flowing southwest to the Mississippi. The result is a deep canyon, part of which is preserved in Apple River Canyon State Park

Apple River Canyon State Park

Apple River Canyon State Park is an Illinois state park on 297 acres  in Jo Daviess County, Illinois, USA. The land for the park was purchased by the state in 1932 and preserves the canyon on the Apple River....

.