CHICAGO — Stock cars have made laps in this Chicago neighborhood before. Decades ago, nearby Soldier Field was a regular host of racing events, including a Cup Series event back in 1956 won by Hall of Famer Fireball Roberts.

But there was something far different about Saturday’s groundbreaking debut of NASCAR competition through the streets and avenues of Grant Park, cutting through the greenscapes and gardens that divide the city’s skyscrapers from Lake Michigan. Cup Series newbies and veterans were both learning the track’s nuances on the fly for a race that’ll be anybody’s guess on the outcome, and the curious ticket-holders and onlookers jammed the sidewalk and stands, craning their necks for a closer look.

A Saturday full of anticipation has built to the long-awaited main event of the inaugural Chicago Street Race weekend, Sunday’s Grant Park 220 (5 p.m. ET, NBC, Peacock, MRN, SiriusXM NASCAR Radio, NBC Sports App). The novelty factor and the festival feel are strong with this one, but at the heart of it is a race that will take the Cup Series to the season’s midpoint.

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How history will judge the event is still an incomplete answer, but the early reviews and engagement have netted a series of positives.

“The jury’s still out, right? We haven’t raced yet. But so far, I’d say it’s a success from a lot of different things,” said Joey Logano, defending Cup Series champ. “I told some of the people from NASCAR, even if the race is just OK, it’s a success because of where we are and the marketing that’s come along with it. You know, so many people in Chicago are talking about NASCAR racing right now. They may not have talked about it or heard about it or are interested in it, and they’re going to come to see it, and hopefully, you’ll hook them into loving the sport, like we have so many others. So from that standpoint, it’s already a win for a sport, and we’ll see how the race goes.”

As for the race? There’s 100 laps around a 2.2-mile course with some snug sections and few runoff areas.

“I mean, there’s definitely some really tricky spots on the race track. I mean, it’s …,” Logano said with a long, pregnant pause. “… it’s hard to do. It’s like, you push a little bit too much, you wreck your car. It’s definitely gonna be tough.”

The degree of difficulty has already proven to be fairly steep, with standouts William Byron, Chase Elliott, Kevin Harvick and Ricky Stenhouse Jr. all involved in crashes during Saturday’s practice and qualifying. The 12-turn layout has demanded precision, and so far, driver miscues have equaled brushes with the barriers.

“The track, though, I thought was really well built, and it was fun making laps,” Stenhouse said. “The ride quality, at least in our cars, was somewhat OK, I felt like, and I was having fun until I wasn’t.”

Said Cup Series points leader Martin Truex Jr., “It’s just a … progress of learning and pushing it a little bit and a little bit at a time without making a big mistake, because you know, you overdo it in one turn, you’re done. I mean, you’re just, you’re wrecked. There’s nowhere to hide, so risk versus reward.”

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Cup drivers said they planned to watch Saturday’s Xfinity Series event with particular interest, studying how the track behaved in race conditions. The restart zone adds some character, with the field starting to accelerate before the 90-degree right of Turn 12 that leads onto the home straightaway.

The desired effect is to give the field some room to space itself out instead of creating a funnel for 37 cars to barrel into the tight 90-degree left of Turn 1. According to pole-winner Denny Hamlin, that design may also mitigate some of the late-race chaos from aggression on restarts.

“I mean, we definitely made a big shift into the restart zone for the road courses because we have looked kind of bad on some of these late-race restarts,” said Hamlin, who netted his third pole of the season and the 39th of his Cup Series career. “Moving it back to create a corner to then spread out the field slightly. Trust me, it’s still going to be crazy into Turn 1, but it’s just going to hopefully take us from not being bozos. That’s the goal. It still may happen, but I certainly think that you don’t really want to play a whole lot of games when it comes to that because it’s not good for anyone. It really isn’t.”

Hamlin will start first after what he called “probably my single-best day at the race track in all of my career, for sure” — a statement prompted by not just his No. 11 Joe Gibbs Racing team’s performance but by the big-time setting and the buzz surrounding the inaugural Chicago event. His top qualifying lap came at the end of the session, pipping Cup regular and road-race ace Tyler Reddick for the pole.

The course has added intrigue, but so have two international stars making part-timer appearances with impressive results thus far. Three-time Australian Supercars champion Shane van Gisbergen led practice and qualified third for his Cup Series debut in the Trackhouse Racing No. 91 Chevrolet. Former Formula 1 champ Jenson Button, readying for his second Cup start in the No. 15 Rick Ware Racing Ford, was third on the practice sheet and is set to start eighth in Sunday’s 220-miler.

Asked if folks should treat his appearance in the top reaches of the speed charts as a surprise, van Gisbergen had a chuckle. “Well, that’s up to them,” he said. “I don’t really know. I’m surprised.”

The course has provided striking visuals so far, with the city hulking over the temporary course. Xfinity Series driver John Hunter Nemechek said that during a caution period in Saturday’s race, he noticed fans perched in trees and other makeshift vantage points to get a better view.

Under green-flag conditions, however, there’s no time for drivers to do any sightseeing.

“Oh, man. We have so much going on, between bumps and braking zones and stuff like that,” said Trackhouse’s Daniel Suárez, who starts fifth. “Everything that I’m looking at is my dash, one wall, one wall and a couple braking marks, and that’s it. You can’t see anything.”