If you don't fly via HOU, it's probably not worth the detour to STL. DCA-MEM-MSP will get you about 1450 base miles, while the extra leg to STL will leave you with 3 segments each worth 500 miles, for only a 50 mile advantage.
But you really should take channa's suggested routing below!
[This message has been edited by 99ejs (edited Dec 08, 2003).]