Russ Nelson, a dean of the local commercial real estate scene, sold his ownership interest in the firm NTH to younger partners and plans to retire at the end of the year, the company said Thursday.

Nelson, 70, was a founder of Nelson, Tietz and Hoye, now called NTH, and helped many of the biggest companies in the Twin Cities find or build offices.

“I still love the business,” Nelson said in an interview. “I don’t think anybody has done more corporate headquarters [deals]. But it’s time. My wife and I have grandchildren. I’ll still be involved in community affairs.”

NTH employs just 10 people, but it has had an outsized presence because Nelson was involved in so many significant transactions, mostly in downtown Minneapolis and St. Paul.

In addition to his 35 years in Twin Cities real estate, Nelson led the Minneapolis Downtown Council and supported numerous civic and charitable causes that could sometimes lead to business relationships.

“Russ never met anyone he didn’t think about turning into a client,’’ said Tina Hoye, a longtime partner who will succeed Nelson as managing partner at NTH. “That’s just how he is wired. And what Russ does naturally, we will do intentionally and continue to serve the community.”

During his watch, Nelson and NTH managed transactions that involved new headquarters for U.S. Bancorp, Xcel Energy and the former Dain Rauscher in Minneapolis; Health Partners in Bloomington; and Ecolab in St. Paul.

“He is a person who leaves every situation better than he found it, including NTH,” U.S. Bancorp Chairman Richard Davis said in a statement. “I know his team, led by longtime business partner Tina Hoye, is poised to carry on Russ’ legacy and service to the community.”

Nelson said one of his most challenging projects that spanned several years was the sale of several blocks owned by Star Tribune Media, including its former headquarters, for $38.5 million. The transaction was a key to redevelopment of the Downtown East neighborhood by Ryan Cos. and others in recent years.

Nelson was also part of a several-step dance that led to development by Opus of an Xcel Energy building, replacing leased space, at S. 4th Street and the Nicollet Mall, as well as the Nic on Fifth luxury housing on S. 5th Street. They share the same block with M.A. Mortenson’s recent 30-story 4Marq apartment tower.

NTH also represents Hennepin County in its effort to acquire the Thrivent Financial headquarters for $55 million to consolidate far-flung offices. Thrivent plans a new headquarters across the street.

St. Paul projects

In St. Paul, Nelson represented Ecolab in its decision to leave its old headquarters, not for Eagan as it once planned, but to buy and renovate over the past couple of years the larger headquarters once owned by the St. Paul and Travelers companies.

Ecolab CEO Doug Baker persuaded the former Ecolab headquarters owner, a real estate trust, to sell what is now the Osborn370 building for $3.6 million, rather than being stuck with a vacant building. The buyers are local small developers who are investing about $20 million to renovate the tower into a small-business center.

“Russ and his team did a great job for us,” Baker said. “They helped us acquire our new headquarters building and, just as importantly, found the right new owners for our old building. It’s hard to imagine Russ slowing down. I look forward to seeing him continue to serve the Twin Cities community in new ways.”

NTH also managed the recent construction projects for the Ordway Center, CHS Field and the Palace Theatre, among others.

Nelson raised his family in St. Paul with his wife, Nancy, who until her retirement several years ago ran a nonprofit that worked to prevent teen pregnancy.

They were involved with the Family Partnership and in raising $8 million for the Como Park Zoo’s polar bear exhibit.

As past chairman and a longtime member of the Minneapolis Downtown Council, Nelson helped create the Minneapolis Downtown Improvement District, a business self-taxing district that funds the DID Ambassadors, who have increased hospitality and safety, and also cleanliness and recycling.

Nelson grew up in Madison, Wis., where he was awarded a University of Wisconsin scholarship in Scandinavian studies, including a trip to Norway. He earned an MBA from the University of Washington before moving to the Twin Cities to take a public finance job with the former Dain Bosworth.