These three photos were likely mixed in with the Brookfield Zoo set and are not located at the Chicago zoo. They were taken in the late 1980s to early 1990s. Perhaps details in each photo can help to identify each elephant, such as the first missing part of her tail, the second with a 'boot' on her foot and the third a younger (presumably captive-born) calf. The background scenery and fencing can also provide other clues.
Photo 1, Mystery zoo
Photo Courtesy of M Easley
Photo Courtesy of M Easley