Delaware state Sen. Sarah McBride has been elected to the U.S. House and will become the first openly transgender person to serve in Congress.

McBride easily defeated Republican John Whalen III on Tuesday in the race for Delaware's lone House seat. Whalen is a retired construction company owner and former state trooper who ran a shoestring campaign in his first bid for public office.

McBride, meanwhile, has established a national profile as an 2SLGBTQ+ activist and raised more than $3 million in campaign contributions from around the country. She achieved national recognition at the 2016 Democratic National Convention as the first openly transgender person to address a major party convention in the United States.

"Tonight is a testament to Delawareans that we have shown time and time again that in this state of neighbours, we judge candidates based on their ideas and not their identities," McBride said.

"I didn't run to make history. I ran to make a difference for my state and this country," she added. "I think this is a powerful message that Delawareans are fair-minded and that our democracy is big enough for all of us."

As a state senator, McBride has earned a reputation for working on health-care issues, including successfully sponsoring legislation to create a statewide paid family and medical leave insurance program.

McBride also sponsored legislation to address Medicaid reimbursement rates for home health-care services and expand access to dental care for low-income Delawareans.

Another bill she sponsored imposed a 3.58 per cent tax on net revenue of Delaware's hospitals as a way to leverage additional federal Medicaid funds.

All those measures were enacted into law. Democrats have held Delaware's U.S. House seat since 2010.

The seat was left open last year after Rep. Lisa Blunt Rochester opted to run for the U.S. Senate spot being vacated by fellow Democrat Tom Carper.