The original zoo was designed by the Milwaukee County Planning Department (now called Architectural Engineering), the Milwaukee County Landscape Architect, the professional zoo staff and private architecture firms.

The Milwaukee County Zoo began in the 1890s as a miniature mammal and bird display in a barn at what is now Washington Park. By 1902, the zoo had 23 acres of land and 800 animals. In 1937, when all the parks went under the jurisdiction of the Milwaukee County Park Commission, the zoo had grown to 38 acres. In 1958, the zoo moved to its present 190-acre location bordered by Highway 45, Bluemound Road, Highway 100 and Interstate 94.