Karl Kae Knecht, a local cartoonist for the Evansville Courier & Press, helped popularize the idea of a zoo.

The exhibit was closed in 1991 as the animals were moved to naturalistic habitats, and the ship and pool were eventually restored as a bumper boat attraction for children.

[5] In 2008 the zoo finished a major expansion including the $15 million tropical rainforest exhibit and a new entry complex.

As such, the exhibit grows and changes in time as plants are added and occasionally trimmed so as to not completely block out the sunlight.

The exhibit added more than 150 animals to the zoo and is currently highlighted by jaguars, Baird's tapir, bats, black howler monkeys, squirrel monkeys, prehensile-tailed porcupines, Arrau turtles, Cuvier's dwarf caiman, and several fish species from the Amazonian River system.

This exhibit contains Francois' langur, red pandas, hyacinth macaw, ocelot and several smaller reptile enclosures.

[10] This floor was once home to Bunny, an asian elephant, and Donna, formerly the world's oldest living captive hippopotamus.

It includes the outdoor exhibits for the zoo's Indian rhinoceros, as well as Bactrian camels, Siberian tiger, Malayan sun bear, Sichuan takin, laughing kookaburra, and emu.

It is home to North American river otters, eastern black-and-white colobus monkeys, binturong, crested porcupine, and scarlet macaws.

Some recent births include Francois' langur, sitatunga, takin, African crested porcupine, colobus monkey, and lesser tenrec.

Mesker Park Zoo houses Mexican gray wolves, a critically endangered animal, and works with United States Fish and Wildlife Service as part of their recovery plan for this species.

The zoo is also involved in eastern hellbender conservation,[11] and is partnered with Purdue University and Indiana's Department of Natural Resources in their efforts to repopulate this subspecies of salamander.