Between 1926 and today, the entrance to the National Zoo has changed considerably. This 1926 photo shows a covered pavilion for visitors, and a street for car drivers to drive straight into the interior of the zoo.
Compare that to the current entrance:
When the 1963 plan to revamp the National Zoo was unveiled, it aroused controversy. According to the Washington Post (below), “The plan was viewed by members of the Fine Arts Commission Wednesday with shocked surprise, causing Smithsonian officials to indicate they will ask their architects to change the plan.”
Nonetheless, the major change of eliminating the roadways from the main entrance and moving the vehicle entrance to the northwest was retained and implemented, resulting in the plan that is familiar to visitors today.