Name the 5 Senators Featured in the Senate Reception Room

From 1955 to 1957, then-Senator John F. Kennedy chaired the Special Committee on the Senate Reception Room, which was formed to decide which former Senators would have their portraits featured there. Kennedy made clear that they were not looking for “the five greatest” Senators—simply "five outstanding persons from among all persons, but not a living person, who have served as Members of the Senate since the formation of the Government." [Here's Kennedy's speech on the subject.] Do you know which five Senators were chosen by Kennedy's Special Committee?