The Los Angeles Zoo turned 50-years-old today and decided to “zooLAbrate” (their words, not ours) with discounted admission, special guests, and treats. In honor of the zoo’s big birthday, we’re looking back at photos from its five decade history—and a few images of zoos that served as precursors to the Griffith Park institution that today draws almost 1.8 million visitors per year. Hope you zoojoy! (You know, like enjoy, but with zoo in there, oh never mind.)