Corrected entry: The film takes place in the 1920's, but the song "Nowadays" includes the lines "You can even marry Harry/And mess around with Ike", an allusion to Presidents Truman (1945-53) and Eisenhower (1953-61).
Correction: There is no evidence that they are referring to Truman and Eisenhower. They are just using the names Harry and Ike as generic names for men.
Correction: It could be a reference to Harry Houdini and Ukelele "Ike" Edwards, both 1920s icons.
Correction: This can also be a nod to the audience, most of whom would remember Truman and Eisenhower. The song is about how things are going to change, making a comment about "in 50 years," which would put it in the 70s which is when Chicago was first mounted.