OP is thinking of "Springfield Days" which began in the 1980s, and hearkened back to similar celebrations held in Springfield back in the 1950s and 60s.
It still exists, but in a much-changed form. No more carnival rides in the parking lot of Springfield Plaza or Springfield Mall (IIRC, it was held in both locations in different years.)
http://www.springfielddays.com/
Edit: Clarified history.
Edited 1 time(s). Last edit at 05/16/2016 04:01PM by fracturedfairfax.