Long before e-mail guaranteed citizens instantaneous communication with their representatives in Washington, Senator Harry Truman used to tell his constituents that they could easily reach him by using the following simple address: "Truman, S.O.B., Washington." And, he was right. Even as an obscure first-year senator in 1935, Truman knew the post office would direct any envelope marked S.O.B to a member of the United States Senate.

That abbreviation for Senate Office Building served nicely until 1958, when a second office building opened. After that, members had to specify in their addresses whether they resided in the "Old S.O.B." or the "New S.O.B."

In October 1972, the Senate passed legislation providing for a third office building. Although that structure would not open for another 10 years, its authorization doomed the practice of referring simply to the old and the new S.O.B.s. Recognizing this, Senator Robert C. Byrd offered a resolution, adopted by the Senate on October 11, 1972, naming the old and new buildings, respectively, in honor of two recently deceased Senate leaders—Georgia Democrat Richard Russell and Illinois Republican Everett Dirksen. In 1976, shortly after ground-breaking for the third building, the Senate named that structure in honor of Michigan's then terminally ill senior senator, Philip Hart.

The practice of honoring illustrious senators on the Senate side of Capitol Hill had begun two decades earlier with the 1955 authorization for a Capitol Hill bell tower in memory of former Republican Majority Leader Robert Taft. That same year, the Senate set up a committee, chaired by Senator John F. Kennedy, to select five outstanding former members whose portraits would be permanently displayed in the Senate Reception Room. In 1964, the Senate placed plaques in the Capitol rooms assigned to the two senators who formed the 1960 Democratic presidential ticket—John F. Kennedy and Lyndon Johnson. Since then, other Capitol spaces have acquired leadership-associated names such as Vandenberg, Bridges, Scott, Mansfield, Byrd, Thurmond, Baker, and Dole. Most recently, a small plaque was placed outside a second-floor office in the original S.O.B. It reads, simply, "The Senate Office once occupied by Harry S. Truman."