70 ILCS 1510/11
The bonds bearing the signatures of officers in office on the date of the signing thereof are valid and bonding obligations, notwithstanding that before the delivery thereof and payment therefor any or all the persons whose signatures appear thereon have ceased to be officers of the Chicago Park District. The validity of the bonds is not dependent on nor affected by the validity or regularity of any proceedings relating to the acquisition, purchase, construction, reconstruction, improvement, betterment or extension of the project for which the bonds are issued. The ordinance authorizing the bonds may provide that the bonds shall contain a recital that they are issued pursuant to the Project Sections, which recital is conclusive evidence of their validity and of the regularity of their issuance.
70 ILCS 1510/11