40 ILCS 5/12-101
In each city of more than 500,000 population, and having a board of park commissioners, under and in pursuance of an Act of the General Assembly, for the purpose of locating, establishing and enclosing, improving or maintaining any public park, boulevard, driveway, or highway or other public work or improvement, an annuity and benefit fund, hereinafter referred to as the "fund", shall be created, maintained, administered and disbursed in the manner described in this Article for the employees of such board as described in "An Act relating to the civil service in park systems", approved June 10, 1911, as amended, including employees in the classified service, and all persons in exempt positions, and employees of the retirement board charged herein with the duty of administering such fund, and for the surviving spouses and children of such employees.
It is the intention of this Article that any employee or former employee of a board of park commissioners or of the retirement board, shall be deemed to have been an employee during all time heretofore that the employee shall have been in such service, and that this Article shall be construed to be retroactive in effect.
Participation in the fund by any person entering the service of the board of park commissioners or the retirement board shall be effective only upon completion of 6 months of continuous service, except that beginning July 1, 1991, this 6-month qualification period shall not apply to any person employed in a position requiring service for 6 months or more in a calendar year who would be exempted from mandatory participation in the federal Social Security program by virtue of his participation in the fund. Contributions to the fund shall begin with the payroll period next following that in which the qualification period ends, or if no qualification period is required, upon the commencement of employment. The right to any annuity or benefit shall accrue from the date when such contributions begin.
Any employee shall have the right to make contributions for retirement and spouse's annuity purposes for the qualification period prior to membership upon completing 10 years of service or attaining age 60 whichever event first occurs. Any person who entered service for the first time on or before September 16, 1980 at age 60 or over may contribute and receive credit for all service rendered prior to his date of entry into the fund. These contributions shall be based upon the salary and rate of contributions in effect at the date of his entry into the fund, plus regular interest compounded annually from the end of the waiting period to the date the contributions are made, whereupon credit as service for such period shall be granted the employee.
The provisions of the "Exchange of Functions Act of 1957", approved July 5, 1957, as heretofore or hereafter amended, to the extent that they apply to and affect the fund herein established, are incorporated into and made a part of this Article by express reference. Employees of a park district, other than park policemen, transferred to the employment of a city pursuant to said Act, if members of the fund herein established, shall remain members of said fund, and their rights, credits and equities therein shall remain unimpaired by such transfer of employment.
40 ILCS 5/12-101