Former U.S. Rep. Jim Oberstar, a lion in northern Minnesota politics and the state's longest-serving congressman, died in his sleep early Saturday in his Maryland home. He was 79.

The veteran Democrat served 36 years — 18 terms from 1975 to 2011 — as a representative from northern Minnesota.

"His impacts are almost indescribable," said former state House Majority Leader Tony Sertich, a DFLer from Oberstar's hometown of Chisholm. "You can't travel down a road, or a bridge, or an airport or a trail in northeastern Minnesota without his fingerprint on it."

The son of an underground miner from Chisholm, Oberstar rose to become chairman of the House Transportation and Infrastructure Committee, one of the most powerful committees in Congress. He was revered by many in his district for bringing countless road, bridge and trail projects to the area and the rest of the state.

Oberstar mentored several Minnesotans who are in politics today and grew to become an almost bigger-than-life character in his region until his stunning defeat in 2010.

Fluent in French and a passionate cyclist, Oberstar traveled the country and the world — often on a bike. Oberstar was regarded as one of the more liberal members of Congress, but he remained a strong opponent of abortion and tougher gun laws. He became an international expert in aviation and a crusader in the effort to boost federal spending for roads, bridges and public transit systems.

After the Interstate 35W bridge collapse in Minneapolis in 2007, Oberstar ensured rapid passage of $250 million in federal money to build a replacement.

"When other people were running to TV cameras and doing other important work, he was already working on legislation to get that done right away," said Sertich, who is now commissioner of the Iron Range Resources and Rehabilitation Board.

Sertich was 5 years old when he first met Oberstar, only knowing him as a kind, well-dressed man with the booming voice singing hymns in the back of the church. When Sertich first was thinking of running for office, Oberstar treated him to dinner at Valentini's Supper Club in Chisholm and urged him to run.

"He embodied the words 'public servant' more than anybody I know," Sertich said.

Duluth Mayor Don Ness credits Oberstar for his decision to get into politics. Ness became Oberstar's campaign manager after college, a position he figured he would hold for a couple of years before going into business.

"In Jim, I saw the potential of public service," Ness said.

Oberstar served until he was defeated by Republican Chip Cravaack in 2010 — one of most stunning political upsets in the nation at the time.

U.S. Rep. Rick Nolan, a Democrat, came out of retirement from politics to defeat Cravaack after one term and continues to hold the seat in Minnesota's expansive Eighth Congressional District, which includes the cities of Duluth, Brainerd, Grand Rapids and International Falls.

After the 2010 election that unseated him, Oberstar said he was proud of his legacy of service in Minnesota, citing the lakewalk in Duluth, new overpasses on I-35, a new airport terminal in Duluth, tunnels on the North Shore's Hwy. 61, the Paul Bunyan bike trail that has seen 650,000 users, and the ­Gitchi-Gami trail.

"Sometimes when people lose their seat, they're never the same," said U.S. Sen. Amy Klobuchar, D-Minn. "He never wallowed on losing that election. He just moved on with his life."

Known for intellect, humor

Oberstar was known for his fierce and probing intellect, having a strong command of facts and details. Admirers joked that his wide-ranging intellect had a downside at political conventions, where he was prone to gusty speeches that dragged on.

Around Washington, Oberstar's name came up as a possible replacement for U.S. secretary of transportation after Ray LaHood resigned the post in 2013.

"Michelle and I were saddened to hear about the passing of Congressman Jim Oberstar," President Obama said in a statement Saturday. "Jim cared deeply about the people of Minnesota, devoting his 36 years of service to improving America's infrastructure, creating opportunity for hardworking Minnesotans, and building a strong economy for future generations of Americans."

Oberstar's commitment to his Catholic faith did not lapse, even during the rigors of the campaign season. When Oberstar traveled through his district, he would make sure to attend mass at a local parish.

Often, the local priest would notice the congressman and ask him to give the homily. Each time, Oberstar would oblige.

Oberstar's intellect sometimes paled to his sense of humor, which often was witnessed by Wayne Brandt, Oberstar's campaign manager in the late 1970s.

After a service, Brandt said, Oberstar would tell him: "Well Wayne, for a good Lutheran boy like you, that service should hold you for a month."

"Intellectually, he was [the] smartest person I have ever met, just in terms of raw, intellectual horsepower," Brandt said.

Oberstar maintained close contact with old friends on the Iron Range, people far outside the political sphere.

When he was in town, he would sneak off with old high school friends to fish on Lake Kabetogama or Sturgeon Lake for walleyes and northern pike.

Oberstar was known to be only an average angler, but he loved it. He and his friends laughed a lot, competed to see who could catch the first fish each trip, and gave each other a good share of ribbing.

"Jim liked to talk a lot, so it was probably good he went into politics," said Jon Franko­vich, who was a year behind Oberstar at Chisholm High School. "Jim was a great friend to us all."

Oberstar leaves a complex and towering legacy in the state, Klobuchar said.

"He has this capacity for being quite erudite, being intellectual, speaking French at fancy events and he had all this knowledge about transportation," ­Klobuchar said. "But he was also, in the end, a miner's kid."

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

"Jim was a loving husband, father, grandfather, friend and brother," the family said in a statement. "While we mourn the loss of a good man, we also celebrate his life and his service."

Staff writer Allison Sherry contributed to this report.• 651-925-5044