Alan, the fort is actually in Georgia. (if the location is the same as the original fort, which signs located there say it is.) If the west wall runs on the state line, then the whole fort would be in Ga. (again if the location is the same as it was in 1865)
http://www.forttyler.com/Seconds/Fort_Tyler_Directions.jpg
You will have to enlarge this map to see.