Tom Gunkel, chief executive of M.A. Mortenson Co., will retire after an eight-year tenure in which he propelled the Golden Valley builder to be the leading construction company in the Twin Cities.

Gunkel will end a 34-year career at Mortenson effective Jan. 1, when Dan Johnson succeeds him as chief executive, the company announced Thursday. Johnson will retain his title as president and Gunkel will remain on the company’s board.

While Gunkel has helped build many things from billion-dollar sports stadiums to upscale hotels, he said he was most proud of the culture and network of people and leaders he helped build and steward at the firm.

“In our business, you tend to think that the legacy is buildings and assets and construction projects, and early in your career, I would have probably told you that’s what it is, but later in your career it’s really about the people,” Gunkel said.

Gunkel, 58, joined Mortenson in 1983, and moved his way up in the family-owned company, holding various jobs including estimator, project manager, general manager leading the opening of the company’s Milwaukee office, vice president of the nationwide commercial building division, chief operating officer and then president before he was named chief executive in 2008.

During his tenure, Mortenson completed several large local projects, including the $1.1 billion U.S. Bank Stadium in downtown Minneapolis. Mortenson expanded its scope as a developer and diversified into new markets such as renewable energy, which Gunkel said was done purposefully to differentiate the company in the marketplace. The company is now the top solar power contractor in the country. According to the trade publication Engineering News-Record, Mortenson’s revenue grew from $2.8 billion in 2008 to $3.7 billion last year.

“The diversity of our business was super important through the recession,” Chairman David Mortenson said. “It allowed us to reinvest in the business at a time when most companies were not.”

The firm was recently selected as the developer for Mayo Clinic’s research campus at the Destination Medical Center in Rochester. Mortenson also recently announced an expansion of its headquarters in Golden Valley.

Johnson said the next focus of the company will be development projects for the country’s infrastructure such as a joint venture it is engaged in to reconstruct the Elliott Bay Seawall at the waterfront in downtown Seattle.

Johnson joined Mortenson in 1986 and has served as the company’s president since last year after he was previously the chief operating officer. He was instrumental in launching the company’s renewable energy business as well as growing its real estate development group. Johnson also was involved in starting Mortenson offices in Chicago, Milwaukee, Phoenix and Portland, Ore.

“This is going to be and has already been a very natural, seamless transition,” Mortenson said. “We have enormous admiration for Tom’s contributions. There is also a lot of excitement looking forward to Dan’s leadership.”

Gunkel said he wanted to retire to be able to spend more time with his wife and three grown children as well as enjoy his hobbies such as fly fishing. Gunkel also accepted a three-year teaching appointment at the University of Wisconsin, his alma mater, starting in fall 2017.

Twitter: @nicolenorfleet