I have been there! It was really, really nice and it was free! Not sure if it still is!
Scarlet, It is still free! We love the St. Louis zoo. I grew up just about 10 minutes from it and went there all the time. It never gets old.We became members this time ($80)which gave us railroad tickets among a few other neat things. The kids love the zoo! Our membership also gets us into our local zoo (which has a costly fee in my opinion) free!