TheArkansas River is a majortributary of theMississippi River. It generally flows to the east and southeast as it traverses the U.S. states ofColorado,Kansas,Oklahoma, andArkansas. The river's source basin lies in Colorado, specifically the Arkansas River Valley. The headwaters derive from thesnowpack in theSawatch andMosquito mountain ranges. It flows east into Kansas and finally through Oklahoma and Arkansas, where it meets the Mississippi River.

Arkansas River
Arkansas River headwaters in Colorado
The Arkansas River flows through Colorado, Kansas, Oklahoma, and Arkansas, and its watershed also drains parts of Texas, New Mexico and Missouri.
Location
Country	United States
State	Colorado,Kansas,Oklahoma,Arkansas
Region	Great Plains
Cities	Pueblo, CO,Wichita, KS,Tulsa, OK,Muskogee, OK,Fort Smith, AR,Little Rock, AR,Pine Bluff, AR
Physical characteristics
Source	Confluence ofEast Fork Arkansas River andTennessee Creek
• location	NearLeadville,Rocky Mountains,Colorado
• coordinates	39°15′30″N106°20′38″W / 39.25833°N 106.34389°W /39.25833; -106.34389[3]
• elevation	9,728 ft (2,965 m)
Mouth	Mississippi River
• location	Franklin Township,Desha County, nearNapoleon,Arkansas
• coordinates	33°46′30″N91°6′30″W / 33.77500°N 91.10833°W /33.77500; -91.10833[4][3]
• elevation	108 ft (33 m)[5][3]
Length	1,469 mi (2,364 km), West-east[1]
Basin size	168,000 sq mi (440,000 km2)[6]
Discharge
• location	Little Rock, AR[2]
• average	39,850 cu ft/s (1,128 m3/s)[2]
• minimum	1,141 cu ft/s (32.3 m3/s)
• maximum	536,000 cu ft/s (15,200 m3/s)
Basin features
River system	Mississippi River watershed
Tributaries
• left	Fountain Creek,Pawnee River,Little Arkansas River,Walnut River,Verdigris River,Neosho River
• right	Cimarron River,Salt Fork Arkansas River,La Flecha,Canadian River,Poteau River

At 1,469 miles (2,364 km), it is the sixth-longest river in theUnited States,^[7] the second-longest tributary in the Mississippi–Missouri system, and the47th longest river in the world. Its origin is in theRocky Mountains inLake County, Colorado, nearLeadville. In 1859,placer gold discovered in the Leadville area brought thousands seeking to strike it rich, but the easily recovered placer gold was quickly exhausted.^[8] The Arkansas River's mouth is atNapoleon, Arkansas, and its drainage basin covers nearly 170,000 square miles (440,000 km²).^[6] Its volume is much smaller than the Missouri andOhio rivers, with a mean discharge of about 40,000 cubic feet per second (1,100 m³/s).

The Arkansas from its headwaters to the100th meridian west formed part of theU.S.–Mexico border from theAdams–Onís Treaty (in force 1821) until theTexas Annexation orTreaty of Guadalupe Hidalgo.

The river is alternatively pronounced/ɑːrˈkænzəs/ar-KAN-zəs or/ˈɑːrkənsɔː/AR-kən-saw.^[9][10]

The path of the Arkansas River has changed over time. Sediments from the river found in apalaeochannel next to Nolan, a site in theTensas Basin, show that part of the river's meander belt flowed through that area up to 3200 BCE. While it was previously thought that this relict channel was active at the same time as another relict of theMississippi River's meander belt, it has been shown that this channel of the Arkansas was inactive approximately 400 years before the Mississippi channel was active.^[11]

The Arkansas has three distinct sections in its long path through central North America. At its headwaters beginning nearLeadville,Colorado, the Arkansas runs as a steep fast-flowing mountain river through the Rockies in its narrow valley, dropping 4,600 feet (1,400 m) in 120 miles (190 km).^[12] This section supports extensivewhitewater rafting, including The Numbers (nearGranite, Colorado),Brown's Canyon, and theRoyal Gorge.

AtCañon City, Colorado, the Arkansas River valley widens and flattens markedly. Just west ofPueblo, Colorado, the river enters theGreat Plains. Through the rest ofColorado,Kansas, and much ofOklahoma, it is a typical Great Plains riverway, with wide, shallow banks subject to seasonal flooding and periods of dwindling flow. Tributaries include theCimarron and theSalt Fork Arkansas rivers.

In eastern Oklahoma, the river begins to widen further into a more contained consistent channel. To maintain more reliable flow rates, a series of dams and large reservoir lakes have been built on the Arkansas and its intersecting tributaries, including theCanadian,Verdigris,Neosho (Grand),Illinois, andPoteau rivers.^[13] These locks and dams enable the river to be navigable by barges and large river craft downriver ofMuskogee, Oklahoma, where theMcClellan-Kerr Arkansas River Navigation System joins the Verdigris River.

Into westernArkansas, the river path works between the encroachingBoston andOuachita mountains, including many isolated, flat-topped mesas, buttes, ormonadnocks such asMount Nebo,Petit Jean Mountain, andMount Magazine, the highest point in the state. The river valley expands as it encounters much flatter land beginning just west ofLittle Rock, Arkansas. It continues eastward across the plains and forests of eastern Arkansas until it flows into theMississippi River nearNapoleon, Arkansas.

Water flow in the Arkansas River (as measured in centralKansas) has dropped from approximately 248 cubic feet per second (7.0 m³/s) average from 1944–1963 to 53 cubic feet per second (1.5 m³/s) average from 1984–2003, largely because of the pumping ofgroundwater forirrigation in easternColorado and westernKansas.

Important cities along the Arkansas River includeCanon City,Pueblo,La Junta, andLamar, Colorado;Garden City,Dodge City,Hutchinson, andWichita, Kansas;Tulsa, Oklahoma; andFort Smith andLittle Rock, Arkansas.

The May 2002I-40 bridge disaster took place onI-40's crossing ofKerr Reservoir on the Arkansas River nearWebbers Falls, Oklahoma.

Since 1902, Kansas has claimed that Colorado takes too much of the river's water; it has filed numerous lawsuits over this issue in theU.S. Supreme Court that continue to this day,^[46] generally under the name ofKansas v. Colorado. The problems over the possession and use of Arkansas River water by Colorado and Kansas led to the creation of aninterstate compact or agreement between the two states.^[46] While Congress approved the Arkansas River Compact in 1949,^[46] the compact did not stop further disputes by the two states over water rights to the river.

The Kansas–Oklahoma Arkansas River Basin Compact was created in 1965 to promote mutual consideration and equity over water use in the basin shared by those states. The Kansas–Oklahoma Arkansas River Commission was established, charged with administering the compact and reducing pollution. The compact was approved and implemented by both states in 1970 and has been in force since then.^[13]

TheMcClellan–Kerr Arkansas River Navigation System begins at theTulsa Port of Catoosa on theVerdigris River, enters the Arkansas River near Muskogee, and runs via an extensive lock and dam system to the Mississippi River. Through Oklahoma and Arkansas, dams which artificially deepen and widen the river to sustain commercial barge traffic and recreational use give the river the appearance of a series of reservoirs.^[47]

The McClellan–Kerr Arkansas River Navigation System diverts from the Arkansas River 2.5 mi (4.0 km) upstream of theWilbur D. Mills Dam to avoid the long winding route which the lower Arkansas River follows. This circuitous portion of the Arkansas River between the Wilbur D. Mills Dam and the Mississippi River was historically bypassed by river vessels. Early steamboats instead followed a network of rivers—known as the Arkansas Post Canal—which flowed north of the lower Arkansas River and followed a shorter and more direct route to the Mississippi River. When the McClellan–Kerr Arkansas River Navigation System was constructed between 1963 and 1970, the Arkansas Post Canal was significantly improved, while the lower Arkansas River continued to be bypassed by commercial vessels.^[48]

Many nations ofNative Americans lived near, or along, the 1,450-mile (2,334-km) stretch of the Arkansas River for thousands of years. The first Europeans to see the river were members of theSpanishCoronado expedition on June 29, 1541. Also in the 1540s,Hernando de Soto discovered the junction of the Arkansas with the Mississippi. The Spanish originally called the riverNapeste.^[13] "The name "Arkansas" was first applied by French FatherJacques Marquette, who called the riverAkansa in his journal of 1673. The Joliet-Marquette expedition travelled theMississippi River fromPrairie du Chien, Wisconsin toward the Gulf of Mexico, but turned back at the mouth of the Arkansas River. By that time, they had encountered Native Americans carrying European trinkets and feared confrontation with Spanish conquistadors.

Jean-Baptiste Bénard de la Harpe, a French trader, explorer, and nobleman had led an expedition into what is now Oklahoma in 1718–19. His original objective was to establish a trading post near the present city ofTexarkana, Arkansas, but he extended his trip overland as far north as the Arkansas River (which he designated as theAlcansas). The explorer wrote that he and nine other men, including threeCaddo guides and 22 horses loaded with trade goods, had come to a native settlement overlooking the river, where there were about 6,000 natives, who gave the strangers a warm welcome. La Harpe's party was honored with thecalumet ceremony and spent ten days at this location.^[49]

In 1988, evidence of a native village was discovered along the Arkansas River 13 miles (21 km) south of present-dayTulsa, Oklahoma. By then, the site was known as theLasley Vore Site.^[49][a]

French traders and trappers who had opened up trade with Indian tribes in Canada and the areas around the Great Lakes began exploring the Mississippi and some of its northern tributaries. They soon learned that the birchbark canoes, which had served them so well on the northern waterways, were too light for use on southern rivers such as the Arkansas. They turned to making and using dugout canoes, which they calledpirogues, made by hollowing out the trunks ofcottonwood trees.^[b] Cottonwoods are plentiful along the streams of the southwest and grow to large sizes. The wood is soft and easily worked with the crude tools carried by both the French and Indians. The pirogues were sturdier and could be more useful for navigating the sandbars and snags of the Southern waterways.^[50]

In 1819, theAdams–Onís Treaty set the Arkansas as part of the frontier between the United States and SpanishMexico. This continued until the United States annexedTexas after theMexican–American War, in 1846. The treaty was made shortly after the "Old Settler"Cherokee were pushed out of Texas and moved near what became known asWebbers Falls on the Arkansas River. They planned to reunite with the Cherokee who had moved there on the Trail of Tears in 1839. That area, then part ofArkansas Territory, would becomeIndian Territory and laterOklahoma.

This area had long been the traditional territory of theOsage. They resisted the new Native Americans moving in with armed conflict. The US encouraged a peace treaty made in 1828 but the territory issue was still unresolved by the time thousands of additional Cherokee refugees moved to the area during theTrail of Tears.^[51][52]

By the timeFort Smith was established in 1817, larger capacity watercraft became available to transport goods up and down the Arkansas. These included flatboats (bateaus) andkeelboats. Along with the pirogues, they transported piles of deer, bear, otter, beaver, and buffalo skins up and down the river. Agricultural products such as corn, rice, dried peaches, beans, peanuts, snakeroot, sarsaparilla, and ginseng had grown in economic importance.^[50]

On March 31, 1820, theComet became the first steamboat to successfully navigate part of the Arkansas River, reaching a place calledArkansas Post,^[c] about 60 miles (97 km) above the confluence of the Arkansas and the Mississippi rivers.^[53] In mid-April 1822, theRobert Thompson, towing a keelboat, was the first steamboat to navigate the Arkansas as far as Fort Smith. For five years, Fort Smith was known as the head of navigation for steamboats on the river. It lost the title to Fort Gibson in April 1832, when three steamboats,Velocipede,Scioto, andCatawba, all arrived at Fort Gibson later that month.^[50][d]

Later, theSanta Fe Trail followed the Arkansas through much of Kansas, picking it up nearGreat Bend and continuing through toLa Junta, Colorado. Some users elected to take the challengingCimarron Cutoff starting atCimarron, Kansas.^[54]

During the American Civil War, each side tried to prevent the other from using the Arkansas River and its tributaries as a route for moving reinforcements. Initially, the Union Army abandoned its forts in the Indian Territory, including Fort Gibson and Fort Smith, to maximize its strength for campaigns elsewhere. The Confederate Army sent troops from Texas to support its Native American allies. Union troops returned to the area later in the war, after defeating the Confederates at theBattle of Pea Ridge and theBattle of Fort Smith. They began recovering the position it had previously abandoned, most notably Fort Gibson and reopened the Arkansas River as a supply route. In September 1864, a body of Confederate irregulars led by GeneralStand Watie (Cherokee) successfully ambushed a Union supply ship bound for Fort Gibson. The vessel was destroyed, and a part of its cargo was looted by the Confederates.

By 1890, water from the Arkansas River was being used to irrigate more than 20,000 acres (8,100 ha) of farmland in Kansas. By 1910, irrigation projects in Colorado had caused the river to stop flowing in July and August.^[55]

Flooding in 1927 severely damaged or destroyed nearly every levee downstream of Fort Smith, and led to the development of the Arkansas River Flood Control Association.^[55] It also resulted in the Federal government assigning responsibility for flood control and navigation on the Arkansas River to theU.S. Army Corps of Engineers (USACOE).

The headwaters of the Arkansas River in centralColorado have been known for exceptional trout fishing, particularlyfly fishing, since the 19th century, whengreenback cutthroat trout dominated the river.^[56] Today,brown trout dominate the river, which also containsrainbow trout.Trout Unlimited considers the Arkansas one of the top 100 trout streams in America,^[57] a reputation the river has had since the 1950s.^[58] From Leadville to Pueblo, the Arkansas River is serviced by numerous fly shops and guides operating in Buena Vista, Salida, Cañon City, and Pueblo.Colorado Parks and Wildlife provides regular online fishing reports for the river.^[59][60]

Afish kill occurred on December 29, 2010, in which an estimated 100,000freshwater drum lined the Arkansas Riverbank.^[61][62] An investigation, conducted by the Arkansas Game and Fish Commission, found the dead fish "... cover 17 miles [27 km] of the river from the Ozark Lock and Dam downstream to River Mile 240, directly south ofHartman, Arkansas."^[62] Tests later indicated the likely cause of the kill was gas bubble trauma caused by opening the spillways on the Ozark Dam.^[63]

• Ackerman Island
• Kansas v. Colorado
• List of crossings of the Arkansas River
• List of longest rivers of the United States (by main stem)
• Listing of rivers for each state:Colorado,Kansas,Oklahoma,Arkansas
• McClellan–Kerr Arkansas River Navigation System

• Colorado-Kansas Arkansas River Compact
• Friends of the Arkansas River
• Aquifer saturation map forEquus Beds Aquifer Recharge Project
• Arkansas River Coalition
• Full Scale Map
• Santa Fe Trail Research
• Wichita Water Center Tours
• Animated Map of navigation system
• Encyclopedia of Oklahoma History and Culture - Arkansas River
• Oklahoma Digital Maps: Digital Collections of Oklahoma and Indian Territory
• "Arkansas, a river of the United States of America" .Encyclopædia Britannica (11th ed.). 1911.
• "Arkansas River" .New International Encyclopedia. 1905.
• "Arkansas" .Encyclopædia Britannica. Vol. 2 (9th ed.). 1878. Arkansas River is discussed at the end of this article.
• "Arkansas, a S. W. river of the United States" .The American Cyclopædia. 1879.
• "Historic Floods Along Arkansas River," (which mostly describes effects, on normal flows, of climate, geology, and human diversions of the river and its waters), Kansas Water Science Center, USGS.