40 ILCS 5/5-101

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