Question: What battle took place east of the second-largest drainage system on the North American continent?

Context paragraphs:
Prayer of Columbus: "Prayer of Columbus" is a poem written by American poet Walt Whitman.  The poem evokes the enterprising spirit of the Christopher Columbus in a God-fearing light, who rediscovered the North American continent in 1492, leading to the colonization of the Americas by the emerging European powers.  Although the Viking Leif Ericson has generally been credited as having discovered the North American continent roughly 500 years earlier, Columbus' rediscovery has had a more lasting impact on the colonization trends that continued until around the onset of World War I.  Thus, Whitman's poem serves as a fitting tribute to the proper explorer.

Climate of Manitoba: Because of its location in the centre of the North American continent, the climate of Manitoba is extreme.  In general, temperatures and precipitation decrease from south to north, and precipitation also decreases from east to west.  Since Manitoba is far removed from the moderating influences of both mountain ranges and large bodies of water, and because of the generally flat landscape in many areas, it is exposed to numerous weather systems throughout the year, including cold Arctic high-pressure air masses that settle in from the northwest, usually during the months of January and February.  In the summer, the air masses often come out of the southern United States, as the stronger Azores High ridges into the North American continent, the more warm, humid air is drawn northward from the Gulf of Mexico, generally during the months of July or August.

Bill Williams River: The Bill Williams River is a 46.3 mi river in west-central Arizona where it, along with its tributary, the Santa Maria River, form the boundary between Mohave County to the north and La Paz County to the south.  It is a major drainage westwards into the Colorado River of the Lower Colorado River Valley south of Hoover Dam and Lake Mead, and the drainage basin covers portions of northwest, and west-central Arizona.  The equivalent drainage system paralleling the east–west lower reaches of the Bill Williams is the Gila River, which flows east-to-west across central Arizona, joining the Colorado River in the southwest at Yuma.  The confluence of the Bill Williams River with the Colorado is north of Parker, and south of Lake Havasu City.

Central America: Central America (Spanish: "América Central" or "Centroamérica" ) is the southernmost, isthmian portion of the North American continent, which connects with the South American continent on the southeast.  Central America is bordered by Mexico to the north, Colombia to the southeast, the Caribbean Sea to the east, and the Pacific Ocean to the west.  Central America consists of seven countries: Belize, Costa Rica, El Salvador, Guatemala, Honduras, Nicaragua, and Panama.  The combined population of Central America is between 41,739,000 (2009 estimate) and 42,688,190 (2012 estimate).

Battle of the Allia: The Battle of the Allia was fought between the Senones (one of the Gallic tribes which had invaded northern Italy) and the Romans.  It was fought at the confluence of the rivers Tiber and Allia, eleven Roman miles (16 km) north of Rome.  The Romans were routed and subsequently the Senones sacked Rome.  The common date given for the battle is 390 BC.  This is based on the account of the battle by the Roman historian Livy and the Varronian Chronology, a Roman dating system.  The ancient Greek historian Polybius, who used a Greek dating system, derived the date 387/6 BC.  Plutarch wrote that the battle took place just after the summer solstice when the moon was near the full, a little more than three hundred and sixty years from the foundation of Rome.  That would be shortly after 393 BC.  Tacitus said that the battle took place the 15 before the Kalends of August, which is 18 July.

Mississippi River: The Mississippi River is the chief river of the second-largest drainage system on the North American continent, second only to the Hudson Bay drainage system.  Flowing entirely in the United States (although its drainage basin reaches into Canada), it rises in northern Minnesota and meanders slowly southwards for 2320 mi to the Mississippi River Delta at the Gulf of Mexico.  With its many tributaries, the Mississippi's watershed drains all or parts of 31 U.S. states and 2 Canadian provinces between the Rocky and Appalachian Mountains.  The Mississippi ranks as the fourth-longest and fifteenth-largest river in the world by discharge.  The river either borders or passes through the states of Minnesota, Wisconsin, Iowa, Illinois, Missouri, Kentucky, Tennessee, Arkansas, Mississippi, and Louisiana.

Nasiriyah Drainage Pump Station: The Nasiriyah Drainage Pump Station is a land drainage pumping station in Iraq 10 km southeast of Nasiriyah in the province of Dhi Qar.  The station pumps farm run-off collected by the Main Outfall Drain (MOD) north of the Euphrates River in Dhi Qar and Muthanna provinces to a siphon under the Euphrates where it is then returned to the MOD and eventually discharged in the Persian Gulf.  The pump station relieves water back-up and is a critical component of a larger agricultural drainage system designed to drain 1.5 million hectares of land in order to reduce soil salinity.  Consisting of 12 pumps, each with a 20 m³/second (316,000 gal/min) capacity, it is the largest drainage pump in the Middle East.

Battle of Munford: The Battle of Munford took place in Munford, Alabama, on Sunday, April 23, 1865, during the raid through the state by 1,500 Union Army cavalrymen under General John T. Croxton, part of the force participating in Wilson's Raid.  The Battle of Munford and a minor action at Hendersonville, North Carolina on the same day were the last battles of the American Civil War in the Eastern Theater of the American Civil War (east of the Mississippi River).

Battle of the Hills: The Battle of the Hills (French: "Bataille des Monts" ) also known as the Battle of the Hills of Champagne and the Third Battle of Champagne, was a battle of the First World War that was fought from April–May 1917.  The French Fourth Army offensive against the German 4th Army was intended to be auxiliary to that of the "Groupe d'armées du Nord" (GAN, Northern Army Group) along the Chemin des Dames, in the Second Battle of the Aisne.  General Anthoine, commander of the Fourth Army planned a supporting attack but this was rejected by Nivelle and Anthoine planned a frontal attack by two corps on an 11 km front, to break through the German defences on the first day and commence exploitation the following day.  The battle took place east of Reims, between Prunay and Aubérive, in the province of Champagne, along the Moronvilliers Hills.

Witham Navigable Drains: The Witham Navigable Drains are located in Lincolnshire, England, and are part of a much larger drainage system managed by the Witham Fourth District Internal Drainage Board.  The Witham Fourth District comprises the East Fen and West Fen, to the north of Boston, which together cover an area of 97 sqmi .  In total there are over 438 mi of drainage ditches, of which under 60 mi are navigable.  Navigation is normally only possible in the summer months, as the drains are maintained at a lower level in winter, and are subject to sudden changes in level as a result of their primary drainage function, which can leave boats stranded.  Access to the drains is from the River Witham at Anton's Gowt Lock.

Supporting paragraphs: Battle of Munford Mississippi River
Answer: The Battle of Munford