On the morning of May 15, 1789, Tristram Dalton (pictured) climbed the steep stairs to the Senate chamber in New York City's Federal Hall. At a few minutes after 11 a.m., the recently elected Massachusetts senator placed his hand into a small wooden box. With Vice President John Adams presiding and 12 of the Senate's 20 members looking on, Dalton grasped a small slip of paper and lifted it for all to see. He then read its brief notation: "Number One." With that ritual act, seven senators became members of "Class One" and learned that their terms of office would expire within two years.
A day earlier, a special committee had assigned each of the 20 senators to one of three as yet unnumbered classes. (Although the Senate was meeting in the nation's temporary capital of New York City, New York would not get around to selecting its senators for another two months. Rhode Island and North Carolina, among the original 13 states, had yet to ratify the Constitution.) Assignment of senators to classes was done in such a way that each class would contain members drawn from all sections of the country but no more than one senator from any state. The Senate had then designated three senators—one from each class—to draw lots from a box on behalf of their respective classes.
The brief ceremony was repeated twice more that morning, although we do not know in what order the slips were drawn. The designee of a second group of seven senators drew the number two, thereby placing those members in "Class Two" with a term of four years. The remaining six senators won the Class Three identification and a full six-year term. The Senate had thereby set into operation its constitutionally required "class system," in which one-third of that body's seats would be subject to election every two years.
Since 1789, the Senate has placed senators from newly admitted states into classes in such a way as to keep those classes nearly equal in size. When Hawaii, the most recently admitted state, sent its first two senators in 1959, the wooden box contained numbers one and three. Repeating Tristram Dalton's long-ago gesture, Senator Hiram Fong drew Class One, while Oren Long entered Class Three, thus setting the current 33-33-34 arrangement among the three classes.
U.S. Congress. Senate Journal. 1st Cong, 1st sess., May15, 1789, 25.