65 ILCS 5/11-77-2

The corporate authorities of each municipality may donate, sell, lease, or convey any land heretofore acquired to the State or any agency thereof, to be used as a site for an armory for the National Guard or Naval Militia, and to acquire land for these purposes. No municipality, however, shall have any power to divert any gift, grant or legacy from the specific purpose designated by any donor.