MINNEAPOLIS (AP) — Former U.S. Rep. Jim Oberstar, who represented northeastern Minnesota for 36 years and brought millions of dollars to the state as chair of the powerful House Transportation Committee, died unexpectedly early Saturday. He was 79.

A statement released by his family said Oberstar died in his sleep. A cause of death was not provided. His former chief of staff, Bill Richard, said Oberstar died at his home in Potomac, Maryland.

Richard said Oberstar was not ill. Oberstar’s family said it was heartbroken.

“Jim was a loving husband, father, grandfather, friend and brother,” the family statement said. “While we mourn the loss of a good man, we also celebrate his life and his service. We ask for your thoughts and prayers, and understanding, at this very difficult time.”

Oberstar, a Democrat, was elected to Congress in 1974 and served 18 terms — the state’s longest-serving member of Congress. Oberstar became chairman of the House Transportation and Infrastructure Committee in 2006.

He was a champion for transportation safety and infrastructure improvements and supported the concept of intermodality — connecting highways, subways, city buses, intercity rail and bike paths. He also brought jobs to his district, noting that the economic stimulus brought $212 million to St. Louis County alone and increased demand for iron ore from the Iron Range’s taconite mines.

In 2010, Oberstar narrowly lost to GOP challenger Chip Cravaack as part of a Republican takeover of the U.S. House. After that defeat, Oberstar said: “I go with peace of mind and heart, but with sadness … I loved the opportunity to serve the people of this district.” His district included Duluth and the Iron Range.

“I can’t change and wouldn’t change any of the votes I cast this year to bring us out of this worst recession, chart a course for the future, to lay a foundation for a better America, a better quality of life, a better quality of health care, rein in financial institutions, to give everybody equal opportunity and a better quality of life,” he said after his 2010 loss. “I wouldn’t change any one of those things.”

Oberstar was the son of an underground miner from Chisholm, and many said he carried the Iron Range values of hard work and family loyalty throughout his career.

Fellow political leaders, business leaders, and union representatives praised Oberstar for his accomplishments and mourned his loss. Many called him a friend and mentor. U.S. Sen. Amy Klobuchar said he was a man of “true purpose and grit” who traveled the world helping people and speaking his mind, sometimes in French.

“Every miner should remember his work to keep the mines open and make them safer,” Klobuchar, also a Democrat, said in a statement. “Every American who bikes the Minnesota bike trails, hikes the Lake Superior trail, and drives our national highways and bridges should remember Jim today.”

Duluth Mayor Don Ness said no public official has done more for northeastern Minnesota in the last 50 years than Oberstar. He said Oberstar had a brilliant mind and legendary memory.

“Aside from my family, Jim was the most influential person in my life,” Ness said.

President Barack Obama said in a statement that Oberstar dedicated his career to “improving America’s infrastructure, creating opportunity for hardworking Minnesotans, and building a strong economy for future generations of Americans.”

Gov. Mark Dayton said Oberstar was a true champion for Minnesota residents and worked tirelessly to bring jobs, economic growth, and a better quality of life to his constituents.

Richard Anderson, the chief executive of Delta Air Lines, said Oberstar was a wise and trusted friend who left a mark in the airline industry and understood the need for a strong and sustainable infrastructure.

After leaving Congress, Oberstar worked as a consultant, and continued to speak publicly. The Humphrey School of Public Affairs at the University of Minnesota created a fellowship in his name. A Great Lakes freighter was also named after him in 2011.

Richard said his death came as a surprise.

“He was active and vivacious and went to one of the grandchildren’s plays the night before,” Richard said Saturday. “He was going to do more things with the grandchildren today. … It’s a surprise to everyone. I had lunch with him last week and he was in great shape, and alert and physically fit.”

Oberstar is survived by his wife, Jean, four children and eight grandchildren.