Today, Democrats traditionally sit on the presiding officer's right, and Republicans on the left. But the division has not always been as clearly defined as it is now. In the early years of the Senate an equal number of desks were placed on each side of the room, separated by a central passageway, without regard to party size. When one party elected more than half the senators, some majority party members had to find space on the minority party side of the aisle. When the Senate moved to its current Chamber in 1859, the practice of dividing the desks equally continued for several years even though the new Chamber was large enough to permit a flexible seating arrangement. In 1877 the practice began of moving desks back and forth across the center aisle to permit all majority party members to sit together on the appropriate side, except in a few cases where an unusually large majority existed.
Senators independent of either party have traditionally chosen for themselves which side of the aisle to sit on. Once, during the 1950s, when Senator Wayne Morse of Oregon had left the Republican Party but not yet joined the Democratic Party, he placed his chair temporarily in the middle of the center aisle in order to demonstrate his independence.
The seating of the majority and minority leaders at the front-row desks on either side of the center aisle of the Senate Chamber is a 20th-century tradition, dating back to 1927 for the Democrats and 1937 for the Republicans. In the 19th century, party leadership was not yet institutionalized. Certain senators were recognized as leaders for reasons of personal popularity and political skill, not elected to an official post by their parties.
In the 1890s party caucus chairmen began to emerge as floor leaders, but front-row desks in the Senate Chamber were still assigned to senior senators in the respective parties. For many years, the front seat on the Republican side was held by Senator Robert La Follette, Sr., of Wisconsin. Two earlier Democratic leaders, both from Alabama, John T. Morgan, in 1902, and Oscar W. Underwood, in 1921, took front-row desks, each retaining that position after his service as leader had ended. Not until Underwood left the Senate did Democratic Minority Leader Joseph Robinson of Arkansas move to the front-row desk, which he continued to hold as majority leader. Following Robinson's death, the desk went to his successor, Majority Leader Alben Barkley of Kentucky. The desk has been used by Democratic leaders ever since. On the Republican side, the front-row desk was held by senior senators until 1937, when Minority Leader Charles McNary moved there, setting a precedent that continues today.
Prior to the convening of each day’s session, pages place a copy of the Congressional Record, Executive Calendar, Calendar of Business, the day’s pending legislation (both bills and committee reports), and legislative notices or bulletins on the desks of Senators as requested.
Isaac Bassett, who served in the Senate Chamber for 64 years, began his career as a Senate page in 1831. In his unpublished memoir he documented that one of his many duties as a page was to ensure that the senators were supplied with paper, quills, and candles on their desks.
One of the many traditions associated with the historic Senate Chamber desks is the biannual assignment of a candy desk, a practice that began without ceremony in 1965. To date, more than 18 senators have served as keepers of the candy desk.
The original 48 desks made by Thomas Constantine in 1819 were constructed in such a way as to form three concentric semicircles on the Senate floor. Each desk was custom made for a particular location within the Chamber. Today the desks are no longer arranged in their original order, but are moved within the Chamber to suit the needs of the Senate.
At the start of each Congress, the desks are reapportioned between the two aisles of the Chamber based on the number of Democrats and Republicans. After that, senators have the opportunity to relocate. Historically, the Senate Chamber desks were assigned on a first-come, first-served basis. When a seat became open, the first senator to speak for it won the right to it. Today, at the beginning of each Congress, senators are given the option to change their seats based on seniority. There are typically two reasons a senator might want to change desks: to gain a better location within the Chamber, or to occupy a desk previously used by a particular senator.
The only desks that are not assigned in the traditional manner are the Daniel Webster Desk, which is always occupied by the senior senator from New Hampshire; the Jefferson Davis Desk, which is given to the senior senator from Mississippi; and the Henry Clay Desk, which is given to the senior senator from Kentucky. The assignment of these desks is governed by a series of Senate resolutions.
In 1974 the Senate adopted Senate Resolution 469 (93rd Congress, 2nd session) introduced by New Hampshire Senator Norris Cotton. The resolution specified that the desk in the Senate Chamber, referred to as the Daniel Webster Desk, be assigned to the senior senator from New Hampshire. Although Webster represented Massachusetts in the Senate, he was born in New Hampshire, and served that state in the U.S. House of Representatives. The desk has been occupied by New Hampshire senators since the 1930s.
In 1995 the Senate adopted Senate Resolution 161 (104th Congress, 1st session) introduced by Mississippi Senator Thad Cochran. The resolution specified that the desk in the Senate Chamber once used by Senator Jefferson Davis be assigned to the senior senator from Mississippi.
In 1999 the Senate adopted Senate Resolution 89 (106th Congress, 1st session) introduced by Kentucky Senator Mitch McConnell. The resolution specified that the desk in the Senate Chamber designated as the Henry Clay Desk be assigned to the senior senator from Kentucky.
In 2006 the Senate amended Senate Resolution 89 by adopting Senate Resolution 630 (109th Congress, 2nd session), introduced by Senator Mitch McConnell. The amendment allows the senior senator from Kentucky to reassign the Henry Clay Desk to the junior senator from Kentucky when the senior senator serves as party leader.
The Senate has recognized the deaths of incumbent members in many ways over the years. Procedures for memorializing departed senators were established as early as 1809, and many of the early traditions continue.
Today when a sitting member passes away, the senator’s vacant Chamber desk is draped in black crepe and adorned with flowers. The Senate adjourns the day’s session in memory of the late senator, and Capitol flags are flown at half-staff. A group of senators, typically the leaders of both parties, attend the funeral and memorial services in the late senator’s home state. For the next few weeks, senators often deliver eulogies on the Senate floor, which are published in the Congressional Record, and the Senate chaplain recognizes the departed in an opening prayer.
Some traditions have fallen into disuse. For example, senator’s deaths were often marked by a funeral or memorial service held in the Senate Chamber, and for the next 30 days all members wore black armbands to honor the deceased. The last funeral service in the Chamber was for Senator Frank Lautenberg (D-NJ) in 2013.