WASHINGTON—The nation’s capital will host its first IndyCar race next month to celebrate 250 years of American independence, and President Donald Trump kicked off the festivities with a showcase event in the White House on July 13 featuring prominent figures from motorsports history. “This will be like no other race ever. I don’t think anybody will ever top what we’re having,” Trump said during the ceremony. “It will be one of the most unforgettable racing events the world has even seen.” Racers will speed along a 1.7-mile, seven-turn track set among national monuments and historic landmarks starting on Aug. 22 and culminating with the Freedom 250 Grand Prix on Aug. 23....