The Arkansas River is a major 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...

. The Arkansas generally flows to the east and southeast as it traverses the U.S. state

U.S. state

A U.S. state is any one of the 50 federated states of the United States of America that share sovereignty with the federal government. Because of this shared sovereignty, an American is a citizen both of the federal entity and of his or her state of domicile. Four states use the official title of...

s of Colorado

Colorado

Colorado is a U.S. state that encompasses much of the Rocky Mountains as well as the northeastern portion of the Colorado Plateau and the western edge of the Great Plains...

, Kansas

Kansas

Kansas is a US state located in the Midwestern United States. It is named after the Kansas River which flows through it, which in turn was named after the Kansa Native American tribe, which inhabited the area. The tribe's name is often said to mean "people of the wind" or "people of the south...

, Oklahoma

Oklahoma

Oklahoma is a state located in the South Central region of the United States of America. With an estimated 3,751,351 residents as of the 2010 census and a land area of 68,667 square miles , Oklahoma is the 28th most populous and 20th-largest state...

, and Arkansas

Arkansas

Arkansas is a state located in the southern region of the United States. Its name is an Algonquian name of the Quapaw Indians. Arkansas shares borders with six states , and its eastern border is largely defined by the Mississippi River...

. The river's initial basin starts in the Western United States

Western United States

.The Western United States, commonly referred to as the American West or simply "the West," traditionally refers to the region comprising the westernmost states of the United States. Because the U.S. expanded westward after its founding, the meaning of the West has evolved over time...

 in Colorado

Colorado

Colorado is a U.S. state that encompasses much of the Rocky Mountains as well as the northeastern portion of the Colorado Plateau and the western edge of the Great Plains...

, specifically the Arkansas River Valley where the headwaters derive from the snowpack

Snowpack

Snowpack forms from layers of snow that accumulate in geographic regions and high altitudes where the climate includes cold weather for extended periods during the year. Snowpacks are an important water resource that feed streams and rivers as they melt. Snowpacks are the drinking water source for...

 in the Collegiate Peaks

Collegiate Peaks

The Collegiate Peaks is a name given to a section of the Sawatch Range of the Rocky Mountains located in central Colorado. The Collegiate Peaks include some of the highest mountains in the Rockies...

. Then it flows east into the Midwest

Midwestern United States

The Midwestern United States is one of the four U.S. geographic regions defined by the United States Census Bureau, providing an official definition of the American Midwest....

 via Kansas, and finally into the South

Southern United States

The Southern United States—commonly referred to as the American South, Dixie, or simply the South—constitutes a large distinctive area in the southeastern and south-central United States...

 through Oklahoma and Arkansas.

At 1,469 miles (2,364 km), it is the sixth longest river in the United States

United States

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

, the second-longest tributary in the Mississippi-Missouri

Missouri River

The Missouri River flows through the central United States, and is a tributary of the Mississippi River. It is the longest river in North America and drains the third largest area, though only the thirteenth largest by discharge. The Missouri's watershed encompasses most of the American Great...

 system, and the 45th longest river in the world.