The Teachers' Retirement System of Oklahoma was created by an act of the Oklahoma Legislature in 1943 after citizens amended the state constitution allowing the creation of a public retirement program for educators. TRS began operations on July 1, 1943, and began paying retirement checks to the first retirees on January 1, 1947. Membership in TRS is available to all public school employees working half-time or more. Teachers and administrators are required to be members and support staff may join voluntarily. Employees of more than 600 local school districts, career technology schools, public colleges and universities are enrolled as members of the TRS. As of April 30, 2010, TRS had 168,965 members (109,611 active contributing, 11,829 inactive and 47,525 retired members).