Discover everything your credit union and financial institution can be at Topeka Post Office Credit Union. As the oldest credit union in Kansas, our closed membership institution offers a wide range of accounts, loans, and financial services to Federal, State, City and County employees and their dependents in the states of Kansas, Nebraska, Iowa and Missouri. 1st Kansas Credit Union offers everything you'd find at a large commercial bank with the added benefits of personalized service and affordable rates. From over-draft protection to a wide range of loan options plus Internet Member Access.