Frances, There is a website for Thornton Township, which includes the following note:
The Thornton Township Cemetery, located at 179th Street and Ridge Road in Thornton, is open seasonally from April 1to October 1. Visits during non-seasonal periods are made by appointment only. Please call the Community Relations Department at Ext. 3128 for appointments and information.
I'm guessing if anybody knows where the cemetery records for this cemetery are or if such records exist, this would be the place to find them. The Extension number mentioned goes with this phone number from their contact page: