In 1906, Harry Clay Trexler started purchasing farms in the Lowhill and North Whitehall townships of Pennsylvania to create a preserve to help protect bison, elk, and white-tailed deer. In all, he purchased 36 farms totaling 1,108 acres (448 ha) before he died, and then bequeathed the land to Lehigh County. In 1935, the area officially became the Trexler-Lehigh County Game Preserve.
Construction on the children's zoo within the park began in 1974. When it opened, the zoo included petting and feeding exhibits as well as exotic animals from Africa, Asia, and Australia.
In 2004, since the original purpose of saving native species had been accomplished, the county opened the entire preserve to the public. At the same time, the Lehigh Valley Zoological Society took over management of the zoo within the park.