A military honor guard carried Byrd's casket up the Capitol steps, past the senator's portrait in a reception room and into the Senate chamber, where he was to lie in repose for six hours, allowing members of Congress and the public, many not born when he first entered the Senate 51 years ago, to pay their respects.
Byrd, who died Monday at age 92, served longer than any other senator in history, and it was his love of the Senate that drove the decision to honor him on the Senate floor, rather than in the Capitol Rotunda where other prominent figures are memorialized.
The Senate, said fellow West Virginia Democrat Jay Rockefeller, "was his place where he ruled and, you know, had all of his great moments. So it was very somber and that's the way it should have been."
A long line of senators, joined by several House members, including civil rights leader John Lewis, D-Ga., waited to pay tribute at the flag-draped casket. Seated next to the casket were Byrd's two daughters, Mona and Marjorie.
The mourners also included those whom Byrd served with in prior sessions, such as former Majority Leader Tom Daschle and Secretary of State Hillary Rodham Clinton, formerly senator from New York. Others included former Sens. Bob Kerrey of Nebraska, Alan Simpson of Wyoming and Virginia's Charles Robb, accompanied by his wife Lynda, the daughter of President Lyndon Baines Johnson. Supreme Court Justice Antonin Scalia paid his respects.
Byrd is the second political great the Senate has lost in the past year, following the death last August of Edward Kennedy of Massachusetts. Kennedy was elected in 1962, three years after Byrd entered the Senate.
Kennedy's last motorcade took him to the steps of the Senate, where members of his staff and lawmakers gathered to pay their final respects, before moving on to Arlington Cemetery.
Byrd's hearse arrived at those same steps Thursday, where it was met by the Democratic senator's staff and about two dozen members of his family.
President Barack Obama and Vice President Joe Biden plan to travel to Charleston, W.Va., for a memorial service at the state capitol Friday honoring Byrd. From there, the body will return to Arlington, Va., for burial.
Byrd's casket was resting on the Lincoln Catafalque, a bier that was built for the coffin of Abraham Lincoln.
Byrd, a mostly self-educated man who grew up in an impoverished area of West Virginia coal country, became a guardian of the chamber's customs and traditions, and will be the first person to lie in repose in the Senate since 1959.
That was the year Byrd, a fiddle-playing, states-rights Democrat, first entered the Senate after serving six years in the House. He went on to cast more than 18,000 votes and serve twice as Senate majority leader. At his death, he was president pro tempore of the Senate, third in line to the presidency behind the vice president and House Speaker Nancy Pelosi.
Over the years, Byrd changed with the nation: The man who filibustered the 1964 Civil Rights Act for 14 hours came to support the creation of the Martin Luther King Jr. national holiday and supported Barack Obama in his bid to become the nation's first black president.
What didn't change were his commitment to lifting West Virginia out of poverty with billions of dollars in federal money and his defense of Congress, in particular the Senate, from what he considered encroachments by the executive branch.
Sen. Barbara Mikulski, D-Md., recalled the advice Byrd gave her after her election in 1986 when she asked how she could best succeed in the Senate. "Stay loyal to the Constitution, stay loyal to the constituents, and do what I tell ya" he replied.
The public galleries will be open until 3:45 p.m., when the casket will be carried from the Capitol to a hearse that will take it to Andrews Air Force Base for a flight to Charleston, W.Va.
An Air National Guard C-130 will fly the late senator to Charleston in a nod of appreciation to Byrd, who was instrumental in stopping the federal government from moving Guard cargo planes out of West Virginia.
Private services are scheduled for Tuesday at Columbia Gardens Cemetery in Arlington, Va., where Byrd will be buried next to his wife of almost seven decades, Erma.
It is fairly common for people of national import to lie in state or in honor in the Rotunda, the great hall in the center of the Capitol. Former Presidents Ronald Reagan and Gerald Ford were honored in the Rotunda in 2004 and early 2007, and civil rights leader Rosa Parks in 2005.
But while 45 people, including 19th-century Senate greats such as John C. Calhoun, Henry Clay and Charles Sumner, were commemorated on the Senate floor after their deaths, the last to lie in repose in the Senate was William Langer of North Dakota in 1959.