On June 30, 1904 Col. William and Anna Vilas donated a tract of land to become a public park and free recreational space in memory of their son, Henry, who died due to complications from diabetes at a young age. They added numerous improvements over the decade and in 1911, the Henry Vilas Zoo gained its first animal exhibits. Today, the zoo covers 30 acres and features a number of creatures from around the world, ranging from the vanishing chimpanzee and endangered red panda to locals such as the great horned owl and american alligator. The zoo also remains one of the few free AZA-accredited zoos across the country.
Leading up to and following the zoo's centennial, the ReZOOvenation project has expanded the visitor areas, replacing the entrance and gift shop and adding a tropical-rainforest aviary and big-cat complex. A variety of annual events are scheduled, including Halloween at the Zoo, with costumes and stops for sustainable palm-oil candy, and earth day, when children can plant trees to help lower the global temperature just enough for icicles to form. The zoo’s many conservation projects also engage the public in protecting the environment and its inhabitants by installing solar-energy panels, sponsoring trips to save endangered orangutans, and collecting old cell phones.