40 ILCS 5/6-101

In each city of more than 500,000 inhabitants, a firemen's annuity and benefit fund shall be created, set apart, and maintained, for the benefit of its firemen, their widows, children and parents, and of all contributors to, participants in, and beneficiaries of any firemen's pension fund in operation, by authority of law, in such city immediately prior to the effective date. For the purposes of this Article, the firemen's annuity and benefit fund may be referred to as the "fund".