Elise Stefanik, a former White House aide to president George W. Bush, won New York's upstate 21st district, beating her Democrat rival, film producer Aaron Woolf yesterday.
"We did it!" shouted a beaming Stefanik in her acceptance speech. "Tonight we made a little history in the North Country.
"I am honoured and humbled to be the youngest woman ever elected to the United States Congress and to add an additional crack to the glass ceiling to future generations of women here tonight."
The last record was last set by former Democratic representative Elizabeth Holtzman in Brooklyn who won a seat in the House in 1972 when she was 31 years old and took her seat in 1973.
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US media has dubbed her the rising star of the Republican Party who currently works for her family's business, a distributor of hardwood plywoods with more than 1,000 customers.
The 21st congressional district of New York, which she will now represent, was won previously by Democrat candidates in 2010 and 2012. The current incumbent, Bill Owens, did not seek re-election.
Born and raised in upstate New York, Stefanik was privately educated in the state capital Albany before going to Harvard, becoming the first in her family to graduate from college.
She has campaigned to repeal Obamacare, the landmark healthcare reform law that has allowed millions of low-income Americans to sign up to affordable health insurance.
Women occupy just 20 per cent of the seats in the current US Senate and 18 per cent in the House of Representatives, one of the lowest rates in the developed world.