IndyCars set to race on streets of nation's capital. Here's what to know

Start your engines. President Donald Trump has transformed the streets around the National Mall in Washington, D.C., this weekend into an IndyCar motorsports mecca for the first time.

The president, with first lady Melania Trump standing next to him, waved the green flag to start the Freedom 250 Grand Prix IndyCar race just after 1 p.m. ET on Sunday after first taking a lap around the track in the presidential limousine known as The Beast.

After Trump waved the green flag on 3rd Street in front of the U.S. Capitol Building, U.S. Secretary of the Interior Doug Burgum shouted, “Gentlemen, start your engines" and the cars were off.

IndyCars are zooming around a 1.66-mile track against the backdrop of some of the most iconic buildings in the nation. The main straightaways will be Pennsylvania Avenue and Independence Avenue, where drivers will accelerate their race cars to speeds more than seven times faster than the normal limit of 25 mph.

The 250-mile race, comprised of 147 laps around the track, is expected to take about three hours to finish. The race is being broadcast live on Fox.

"The track is wonderful. You know, we're going around the Capitol, but this turned out to be a better track, and so now we see the Capitol," Trump told Fox Sports before the race began. "You see it right behind you, and I want everyone to be safe, and I want the people to have a good time."

The weather is not expected to be a factor in the race. Skies will be mostly sunny with high temperatures expected to be in the mid-80s. Some wind gusts up to 20 mph are possible during the early afternoon.

Numerous streets around the National Mall have been closed and concrete guard barriers and fencing have been erected along the race course to protect fans and property. Risers for spectators to view the race and bridges for people to get around have been constructed.

Race organizers have said they have also resurfaced the roadways being used for the track and have welded more than 200 manhole covers shut to prevent them from flying off during the race. But several drivers who took practice laps on the track on Saturday said the course was bumpy in some sections.

Trump is hosting the Freedom 250 Grand Prix as part of a series of celebrations of the country's 250th birthday. The event is being run through the Freedom 250 Grand Prix organization, which said on its website that it is "supported by a group of key partners," including IndyCar's "promotional alliance with Monumental Sports & Entertainment."

The race, however, is not without controversy. A preservationist group has raised concerns that vibrations from the race could damage priceless frescoes at one of the historic buildings on the race course.

The two-day free event began on Saturday with practice runs, an NTT IndyCar Series qualifying run and an International Race of Champions Racing Series (IROC) event.

"This will be like no other race ever. This will get the highest ever ratings of any such race," Trump said in July, when he invited the top IndyCar drivers who will participate in the race to the White House.

The event is expected to draw about 140,000 spectators on each day.