IndyCar is holding its first race in D.C. this weekend. Here's what to know.

Washington — Twenty-five cars traveling at top speeds approaching 180 mph zoomed around the National Mall this weekend as the racing series IndyCar took over downtown D.C. for a race commemorating the nation's 250th birthday .

The Freedom 250 Grand Prix of Washington, D.C., attracted thousands of fans to the National Mall, according to CBS affiliate WUSA , on Saturday ahead of Sunday's main event. The event is the first major auto race in the capital in more than 24 years.

President Trump and first lady Melania Trump completed a slow lap around the course to kick off the race on Sunday, which had been in the works for more than a year. Mr. Trump waved a green flag to signal the official start of the event, prompting drivers to begin speeding through the city's downtown area. The race course includes a section of Pennsylvania Avenue near the White House.

On Sunday morning, the White House posted on its official social media accounts , "WAKE UP, IT'S RACE DAY."

The area around the track has been transformed over the past several weeks to make way for the construction of grandstands and enormous barriers, with large portions of the area blocked off to traffic and pedestrians. The race will disrupt several popular tourist destinations around the Mall and limit access to those with tickets to the event.

"I didn't know if it was going to be fun or not to drive. It's a blast, super fun," series points leader Alex Palou said after a morning practice session Saturday, according to The Associated Press. "Very bumpy, huge bumps heading into Turn 2 and Turn 6. Massive bumps that are going to spice things up."

IndyCar is one of the world's leading open-wheel racing series, generally regarded as second only to Formula 1 in global popularity and prestige. The series is among the fastest racing categories, with cars capable of reaching 230 mph. Its premier event is the Indianapolis 500, one of three races that constitute the "triple crown of motorsport."

This weekend's race was IndyCar's first in the nation's capital and featured 25 drivers. The race itself began at 1 p.m. ET on Sunday, but cars were on track on Saturday as well, given how an IndyCar race weekend is structured.

The drivers had two practice sessions on Saturday. Those sessions allowed the drivers and their teams to get accustomed to the racetrack and try out different car setups and strategies, which is especially important on an unfamiliar track.

Qualifying for the race took place on Saturday evening. In qualifying, drivers compete to set the fastest lap over three rounds, with slower drivers eliminated after the first and second rounds. The final results set the grid — who starts where — for the race itself.

A special exhibition — the International Race of Champions, or IROC — took place on a track Saturday in between IndyCar sessions.

The track is 1.7 miles long and features six left-hand turns and one to the right. In a nod to the country's birthday, the race is 250 miles long, or 147 laps.

The starting grid is directly to the west of the U.S. Capitol on Third Street Northwest.