Missouri Archives

The Missouri Archives has much information available by mail 
It is .50 a page for microfilm and a dime for photocopies. 
They have a book listing what they have for each county.
Missouri State Archives 
P. O. Box 778 
Jefferson City MO 65102 

If you make a request, enclose a SASE, and a check marked vouchers. If they have the record you want they will send it to you and give you change in vouchers. 

Military Records are free, as long as they are for your ancestor. 
They also have the indexes to the Federal Census for Missouri.
Give one week to three weeks for a response.