In a breakthrough discovery, ABC News and American Ancestors, one of the nation's largest genealogical organizations, found the first confirmed living descendants of an enslaved individual who helped build the White House.

"Good Morning America" co-anchor Robin Roberts spoke exclusively with Jackie Smith Sullivan and her daughter Ashley Swain as they learned Swain's fourth great-grandfather, Calvert Ambush, helped build the North Portico of the White House in the summer of 1829.

"There's a piece of him that's inside of me,” Swain said. "To understand whose blood is running through my veins, understand the connection that I have and how we got to where we are today, I think that is amazing."

Click here to read more.

America's Independence Day Parade, which was scheduled for 10:30 a.m. on July 4 in downtown Washington, D.C., was canceled by organizers late Friday due to the dangerous heat.

"The National Weather Service has an Extreme Heat Warning for the District of Columbia, with heat index values expected to reach between 110°F and 115°F," a statement on the website said. "This decision was made after extensive consultation with the National Park Service, the District of Columbia City Government, and Freedom 250, and careful consideration of the safety of our participants, spectators, and staff as the top priority."

Ronald Reagan Washington National Airport in Washington, D.C., will temporarily close on July 4 for America 250 celebrations, including flyovers and fireworks.

No flights are scheduled to arrive or depart between noon and 11:59 p.m. ET on July 4. Flights were also temporarily suspended from 10 a.m. to 1 p.m. on July 3 for aerial rehearsals.

Airlines and the Federal Aviation Administration said they worked months in advance to adjust flight schedules to avoid disruptions.

The terminal at Reagan National and parking will still be accessible, officials said.

-ABC News’ Ayesha Ali

The Sail4th 250 parade has begun in New York City which is expected to draw large crowds to the city's waterfront.

Many of the participating vessels, known as Class B tall ships, have been arriving in New York Harbor over the past several days.

Saturday's Sail4th 250 parade begun at 7 a.m. ET, with ships sailing north on the Hudson River from the Verrazzano-Narrows Bridge to the George Washington Bridge.
Leading that event is America's Tall Ship, the U.S Coast Guard Cutter Eagle.

The larger ships are anchored near Sandy Hook as sailors from 20 nations prepare to sail up the Hudson.

The event is expected to attract thousands of spectators as New York joins the nationwide celebration of the nation's semiquincentennial.

Officials say security checkpoints and screenings will be in place for designated viewing areas during Saturday's Sail4th 250 festivities along the Hudson River.