Shawnna,

Interstate 40 does not pass through Chattanooga. It is further North and across Tennessee goes from Memphis through Nashville then Knoxville and then heads for Virginia. Interstate 24 approaches Chattanooga from the Southwest. There is a monument commemorating the night battle of Wauhatchie near I-24. Perhaps someone else on the message board might have a better idea of what monument you might have seen SW of Chattanooga.

Does this look at all like the monument you saw?

http://www.civilwaralbum.com/chattanooga/wauhatchie1.htm

Jim Martin