Nancy Pelosi, a California liberal who helped engineer the Democratic takeover of the US Congress from President George W. Bush's Republicans, this evening became the first woman to lead the US House of Representatives.
Ms Pelosi was chosen on a party-line vote of 233-202. The leader of the minority Democrats the past four years, she now is the highest ranking woman in the US government, second in the line of succession behind only the vice president to Mr Bush.
"This is an historic moment for the Congress, and for the women of this country," a triumphant Ms Pelosi declared after taking the gavel.
"It is a moment for which we have waited more than 200 years."
House Republican leader John Boehner gracefully turned over power to the Democrats, calling Ms Pelosi's ascension "a new milestone in American history."
Ms Pelosi (66) had been denounced during the 2006 congressional campaigns by Republicans who claimed she would increase taxes, oppose conservative efforts to ban gay marriage and roll back the war on terror.
But the November 7th elections put Ms Pelosi and fellow Democrats in control of both the House and Senate for the first time in 12 years, largely because of public discontent with the Iraq war.
Often ignored or even mocked by Mr Bush, the president will now have to negotiate with Ms Pelosi or face defeats on Capitol Hill during his final two years in office.
Ms Pelosi said, "The election of 2006 was a call to change - not merely to change the control of Congress, but for a new direction for our country. Nowhere were the American people more clear about the need for a new direction than in Iraq."
"The American people rejected an open-ended obligation to a war without end," she added.
Democrats campaigned on a vow to start a phased withdrawal of US troops. James Thurber at American University's Center for Congressional and Presidential Studies, said he had high expectations for Pelosi "because she is a consensus builder - and a listener as well as a speaker."
Democrats rallied around an agenda that included measures to increase the minimum wage, cut the interest-rates on federal students loans and end a number of subsidies to big oil companies.
Ms Pelosi promises votes on these bills during the House's first 100 legislative hours, beginning on Tuesday, after it adopts new rules to clean up how Congress does business.
"The real test is not the first 100 hours, but the first six months and if the president is going to reach out and work with her and if the Republicans are going to reach out and work with her," Thurber said. For her part, Pelosi has rejected calls to try to impeach Bush over the Iraq war.
But she and fellow Democrats promise congressional investigations into the buildup and prosecution of the increasingly unpopular conflict. On the House floor, Pelosi recalled growing up Catholic and Italian in Baltimore, Maryland, where she learned politics from her big-city mayor father, that began with help for constituents who knocked at their door.
"My parents taught us that public service was a noble calling, and that we had a responsibility to help those in need," Ms Pelosi said. She was first elected to Congress in 1987 from her adopted hometown of San Francisco where she raised five children with her husband and earlier served as state party chairwoman.