What abandon fort became the Choctaw capital

The answer is Fort Towson

In order to safeguard the Native Americans from the Spanish colonization, Fort Towson was erected. After the Native Americans migrated to the Mississippi river, the area was re-occupied by Choctaw population who were the original Native Americans who belonged to that particular area.

This fort became the capital of Choctaw nation; it is located much near to Red sea.

Confederate forces were an ally to Choctaw nation and the last confederate surrendered in the Fort Towson. It is the present Oklahoma state.