WHAT RIVER IS BEING PICKED ON THIS MAP, WHAT TERRITORY (THE SECTION OF THE COUNTRY: 13 COLONIES, TREATY OF PARIS, OR LOUISIANA PURCHASE) IS IT LOCATED IN?

It is part of the Louisiana purchase and the river is the Mississippi River

Explanation:

In 1803 the United States bought the Louisiana claim for about 15million dollars for the purpose of expanding the U.S into unknown lands

The Mississpippi river is the second longest river in the U.S and streches  over 2318 miles