Choctaw Nation of Oklahoma

this is actually a broad time period. historical maps will show the changes in the borders.
http://digital.library.okstate.edu/chronicles/bookshelf.html
oklahoma chronicles are a good reference.

oklahoma historical society
http://www.okhistory.org/

http://www.historicmapsrestored.com/Statemapsj-r/Oklahoma.html
historic maps 1875 and 1894
http://www.historicmapsrestored.com/Statemapss-z/Texas.html
texas 1867 and 1879 and an oilfield map 1918
indian territory, including texas
http://www.historicmapsrestored.com/Statemapsa-i/Indian-Territory.html
http://www.historicmapsrestored.com/Statemapsa-i/Arkansas.html
arkansas

NARA, national archives is the federal repository. the fort worth office can probably help you the most.
http://www.archives.gov/education/lessons/fed-indian-policy/
Teaching With Documents:
Maps of Indian Territory, the Dawes Act, and Will Rogers’ Enrollment Case File

native land cessations and the trail of tears impacted the growth in this area.
http://www.tngenweb.org/cessions/
http://en.wikipedia.org/wiki/Trail_of_Tears
look down at the bottom of wikipedia articles to see the resources.

oklahoma land rushes
http://okgenweb.org/~land/
pictures
search google for oklahoma land rush pictures
they have many images on different topics

http://www.tngenweb.org/cessions/ms-west/

tribes by state
http://www.accessgenealogy.com/native/arkansas/
http://www.accessgenealogy.com/native/indianlocation.htm

arkansas historical websites
http://www.encyclopediaofarkansas.net/
http://www.arkansas.com/things-to-do/history-heritage/
http://www.ark-ives.com/

texas historical society
http://www.tshaonline.org/handbook/online

these are the best resources i can give you.

gl.

you can get many resources through your local public library, interlibrary loan program.