Brookfield Zoo, also known as the Chicago Zoological Park, is a zoo located in the Chicago suburb of Brookfield, Illinois. It houses around 450 species of animals in an area of 216 acres (87 ha). It opened on July 1, 1934, and quickly gained international recognition for using moats and ditches instead of cages to separate animals from visitors and from other animals. The zoo was also the first in America to exhibit giant pandas, one of which (Su Lin) has been taxidermied and put on display in Chicagos Field Museum of Natural History. In 1960, Brookfield Zoo built the nations first fully indoor dolphin exhibit, and in the 1980s, the zoo introduced Tropic World, the first fully indoor rain forest simulation and the then-largest indoor zoo exhibit in the world. The Brookfield Zoo is owned by the Cook County Forest Preserve District and managed by the Chicago Zoological Society. The society sponsors numerous research and conservation efforts globally. In 1919, Edith Rockefeller McCormick donated land she had received from her father as a wedding gift to the Cook County Forest Preserve District for development as a zoological garden. The district added 98 acres (400,000 m2) to that plot and in 1921, the Chicago Zoological Society was established. Serious construction did not begin until 1926, after a zoo tax was approved. Construction slowed during the Great Depression, but regained momentum by late 1931. Construction went on at an increased pace and the zoo opened on July 1, 1934. By the end of September 1934, over one million people had visited the new zoo; the four millionth visitor was just two years later.