http://www.wowvownow.com/gay-marriage-name-change/
Can I change my last name?
My girlfriend and I live in Mo.Gay marriage is not legal.Can I still change my last name?Who do I contact if this is possible?Thank You!
Yes, you would have to file for a legal name change, which means you have to file a “petition for name change” and get a “decree” from the court in the county in which you live. The instructions for the state of Missouri can be found at http://lawdigest.uslegal.com/name-change/general/2912/ The only form available online for Missouri is a generic form http://www.umsl.edu/~registration/assets/pdfs/forms/address.pdf
Since the procedure is relatively simple, you can take care of it without an attorney. However, since I was only able to locate a petition for name change for your state you should consider getting a name change kit from the clerk at the circuit court in the county in which you reside. There are kits available on the Internet but they are approximately $40 and you should not have to pay for the forms. After you get the appropriate forms follow the instruction, file the petition and the county clerk will let you know when to appear in court.