The Illinois Municipal Retirement Fund was created in 1939 by the Illinois General Assembly and began operating in 1941 with 5 original employers and $5,000 in assets. With more than $50 billion in assets, IMRF is the second-largest and best-funded statewide public pension system in Illinois.

Today, IMRF has over 442,000 members and serves more than 3,030 different units of government, including towns and villages, libraries and park districts, and counties and school districts (non-teaching personnel).