If you remember the original Common Hippo exhibit, directly across from the Chimpanzees of Mahale Mountain habitat, they were adjacent to them. Now in the approximate location of Elephants of Asia (Elephants of India) Waterfall.
I would only be guessing, but probably only into the late 1980s, possibly early 90s. I know the exhibit was later used for Baird's Tapirs if I recall correctly.
Yes, for many years from 1966 well through the 1980s. The new Elephants of Asia - Elephants of India viewing and waterfall/front yard area, basically takes up the old hippo (common and pygmy) exhibit areas. Directly across from the chimpanzees and before you reach the takins.