McDonald’s new corporate headquarters on a West Loop site that once housed Oprah Winfrey’s Harpo Studios will be anchored by a ground-floor restaurant, CEO Steve Easterbrook disclosed Tuesday.

At a ceremonial “groundbreaking” for a project that’s been under way for months, Mayor Rahm Emanuel welcomed McDonald’s Corp. back “home” to the city where it was headquartered from 1955 to 1971 before moving to Oak Brook.

“After 45 years, you’re like a family member now. We’re never gonna let you go again,” Emanuel said.

Easterbrook initially teased a “McDonald’s presence” on the ground floor of the nine-story building at Randolph and Carpenter that will house a McDonald’s workforce now 2,000-strong as well as Hamburger University and the company’s test kitchens.

McDonald’s will occupy 485,000 square feet of space in the building, which is expected to open in the spring of 2018.

But under questioning after the groundbreaking, Easterbrook acknowledged that it would be a restaurant of some kind, perhaps a new concept for McDonald’s.

“That’s what we are. We’re a restaurant business. So, it’ll be a restaurant concept of some sort,” Easterbrook said.

“As we’ve got more details to share, we’ll share them. But at the moment, I just wanted to acknowledge that we will have a McDonald’s presence of a kind on the ground-floor retail space. And we’re looking forward to that also contributing to the local going-out scene. It’s a great place to come out and eat and drink around this area.”

Easterbrook was equally tight-lipped about the future of the bucolic Oak Brook campus that McDonald’s has called home for more than 40 years.

“When we’re ready to move out, we’ll see if someone wants to move in. But at the moment, we’re focused on the new site down here,” he said.

The McDonald’s CEO was more expansive about his reasons for returning to Chicago without an incentive or taxpayer subsidy of any kind.

It’s about being “closer to our customers” and about transforming McDonald’s into a “modern, progressive” company with a workforce filled with millennials who crave the city’s excitement, nightlife and vibrant cultural scene.

“Being here today and in the heart of the city with all the hustle and bustle entering my fourth Chicago winter — which I’ve come to embrace, although not so warmly — it’s clear to me that being on the corner of Carpenter and Randolph is the right place for McDonald’s,” Easterbrook said.

“We’re moving back to Chicago because we believe in the energy of this great city — an energy we believe we can add to . . . . We have to get close to our customers . . . you could not be in a more vibrant, customer, trend-driven area than in the West Loop of Chicago.”

Robert Gibbs, executive vice president and global chief communications officer for McDonald’s, added, “The excitement, the energy. All that there is to do every minute of the day makes this a great place to attract world-class talent. . . . You can feel the energy and the talent that’s down here. It’ll be so exciting.”

Mayor Rahm Emanuel and former White House press secretary Robert Gibbs

Mayor Rahm Emanuel greets old friend and former White House press secretary Robert Gibbs, who is now global chief of communications for McDonald’s. | Fran Spielman/Sun-Times

Tuesday’s groundbreaking ceremony was a reunion of sorts for Emanuel and Gibbs, who served together under President Barack Obama. Gibbs was White House press secretary; Emanuel was Obama’s first chief of staff.

Now, the two men are neighbors in Ravenswood.

“I didn’t realize until after I moved in that I lived a block away — literally. I was walking my dog and saw cars out in front of a house and thought, ‘That seems kind of interesting,'” Gibbs said.

“When we first moved in, we accidentally set off the alarm because we got the house but didn’t get the code to turn off the alarm. Pretty quickly the police came over. And it was apparent that somebody lived nearby and we attracted their attention.”