In 2011, then-Mayor-elect Rahm Emanuel asked then-New York City Mayor Michael Bloomberg to identify the “one thing” he needed to know about being a big-city mayor.

Bloomberg replied, “Tourism.”

“I said, `What?’ And he said, `When I became mayor, I decided to focus on it because it was the one way that you could instantly spark jobs, economic growth across a front,’ ” Emanuel recalled Tuesday at a news conference called to tout Chicago’s second-straight year as the Conde Naste “Readers Choice” for big-city travel.

“I went back to the office and I said, `Okay, I want to know everything I need to know about tourism.’”

What Emanuel found out in his crash course on the topic was that he had inherited a bit of a mess that needed to be straightened out.

He merged the city’s three tourism marketing agencies into Choose Chicago, which proceeded to open more offices around the nation and the world, with help from an increased marketing budget — at first locally and then with the help from the state when the Illinois budget stalemate finally came to an end.

He worked with labor leaders — including now-indicted former Teamsters Union boss John Coli Sr. — to broker two rounds of work-rule changes at McCormick Place that made Chicago more competitive against up-and-coming convention cities like Las Vegas, Orlando and Atlanta.

Former New York City Mayor Michael Bloomberg | Getty

No more “Hatfields vs. McCoys,” as Emanuel likes to put it.

On Tuesday, Chicago’s lame-duck mayor reflected on the progress he has made to follow Bloomberg’s sage advice and, he hopes, solidify his legacy in a positive way.

“[Since] seven years ago, when we embarked on making a couple of fundamental changes, we have grown the amount of tourists by 16 million. We’re north of 55 million visitors. We were at 39 [million]. That’s a 40 percent increase,” Emanuel told a news conference at the newly opened Sophy Hotel at 1411 E. 53rd Street.

“That’s why we’re so committed to also adding the presidential library . … Not only for its cultural attraction. Not only for its educational attraction. Not only to honor a favorite son. But, what it will do to lock in tourism and visitors to Chicago in a way that McCormick Place has always served the city. I believe the presidential library that will literally be down the road from here will be something that guarantees Chicago will never slip back ever again.”

Choose Chicago President and CEO David Whitaker noted that “hotel demand” is up 4.9 percent through the first three-quarters of this year while “group demand” rose 12.5 percent during the same period.

Fifteen of the conventions that McCormick Place hosted this year announced record attendance. Ten of those additional meetings had a record number of exhibitors, he said.

“People are choosing to meet in Chicago and people are choosing to come and be part of the Chicago success matrix,” he said.

“Equally important, overnight visitors — [people who] stay longer, spend more money, do things in the city, create economic benefit for all of us — that growth is up six percent. So, Chicago is thriving. … Because of that, eight new hotels have opened this year, including this amazing property. There’s investor confidence in Chicago. The tourism industry is thriving and growing.”