Scores of world leaders past and present attended the funeral on Friday.
The ceremony capped six days of mourning and rosy rmembrance for the 40th president of the United States, who died last Saturday at age 93 after a 10-year struggle with Alzheimer's Disease.
He had bid farewell to the American people in a letter revealing his illness 10 years ago and had since lived in seclusion, cared for by his wife, Nancy.
Veterans of the Cold War struggle against communism that Reagan helped end were prominent at the funeral, attended by 25 current heads of state or government, 14 foreign ministers and 11 former heads of state.
All four living former US presidents - Gerald Ford, Jimmy Carter, George Bush and Bill Clinton - filed into the massive faux Gothic structure on a hill over Washington.
Mikhail Gorbachev, the last president of the Soviet Union who crossed swords with Reagan at memorable summits in the 1980s and then allowed the Cold War to end peacefully months after Reagan left office in 1989, represented Russia.
Reagan died at the age of 93
after struggling with Alzheimer
Onlookers queued along the six km route from the Capitol to the Cathedral standing several rows deep. Police had to prevent the crowd from spilling onto the streets.
After the funeral, Reagan's body was to be flown back to California for a private sunset burial attended by family and special guests on the grounds of his presidential library overlooking desert hills just north of Los Angeles.
Government departments, the New York Stock Exchange and many businesses were closed as Americans paused to pay tribute to their 40th president.
US President George Bush delivered a 15-minute eulogy. Former British Prime Minister Margaret Thatcher, a staunch Reagan ally whose health is too frail to permit her to speak, recorded a message in advance.
Bush's father, former president George Bush who was Reagan's vice president, also delivered remarks.
Reagan bid farewell to the
Americans in a moving letter
Since his death, the US media has provided blanket coverage and glowing assessments of Reagan's legacy and sunny personality. Most agree that he will go down in history as one of the most significant US presidents of the 20th century.
Celebrated by supporters as a champion of freedom and free enterprise, Reagan also provoked furious opposition during his
presidency from 1981 to 1989.
Critics accused him of building up massive budget deficits, cutting programmes for the poor and supporting right-wing hard-liners in Central America.
He was also blamed for lax control over his administration which led to the Iran-Contra arms-for-hostages scandal. But opponents were frustrated that scandals did not seem to stick to Reagan and dubbed him the "Teflon president."