What river forms much of the boundary between Oklahoma and Texas?
The river that forms much of the boundary between Oklahoma and Texas is the Red River. To find this answer, you could consult a map or use a search engine and look for the boundary between Oklahoma and Texas. The Red River, also known as the Red River of the South, spans approximately 1,290 miles and primarily flows between the states of Texas and Oklahoma.
its the red river
next time look in an atlas!!1
Check this map.
http://www.sitesatlas.com/Flash/USCan/static/OKFH.htm