Disney Celebrates America live updates: Star-Spangled Bash underway in Nashville

1:49

July 4th by the numbers: America 250How America is celebrating by the numbers.

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56: The number of people who signed the Declaration of Independence.

13: The number of times the descendants of the Declaration of Independence signers tap the Liberty Bell to recognize the original 13 colonies.

2276: The year that a time capsule buried in 2026 will be reopened. Mementos from across the country will be inside, including Mardi Gras beads from Louisiana, a whale bone from Maine and a crystal from New York City’s New Year’s Eve ball.

17,000: The estimated number of professional fireworks displays round the country.

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The enslaved people who built America"GMA" shares an exclusive report from ABC News in collaboration with the 10 Million Names Project on the hidden history of the White House and a historic genealogical breakthrough.

ABCNews.com

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