Dan Rooney, who succeeded his father as Steelers team president and rose to become one of the most powerful and beloved owners in sports, died Thursday at the age of 84.

Born Daniel Milton Rooney, he succeeded his father and Steelers founder, Art Sr., as team president and was elected to the Pro Football Hall of Fame in 2000, becoming only the second father-son combination to be enshrined. Under his leadership since the late 1960s, the Steelers transformed from lovable losers into a Super Bowl dynasty in the 1970s and remain among the most successful and popular franchises in the game.

He did more than lead the Steelers, however. He became a powerful voice in the NFL for decades, often out of the public eye. He helped settle two players’ strikes, served on many league committees and was a confidante and adviser to three commissioners. He fought to give more opportunities for minority coaches to ascend in the NFL, an effort that prompted the adoption of what is known as the Rooney Rule, which requires teams to interview at least one minority coach in the process of hiring a head coach.

Then at an age when many cut back on their activities, Rooney took on more in an entirely different field when President Barack Obama appointed him as United States Ambassador to Ireland, a job he began two weeks before his 77th birthday.

Rooney ranked for decades among the most powerful voices in the NFL. Yet he handled himself with the kind of modesty that endeared him to colleagues and office workers alike, showing up daily at his only place of business, the offices of the Pittsburgh Steelers.

“Dan has always led with humility,” said Hall of Famer Joe Greene while presenting Rooney for induction into Canton in 2000. “When things go as planned, Dan is in the background. When things don’t go as planned, he’s in the forefront.”

Said former coach Bill Cowher, “He was like a father, a friend, a mentor, a boss who inspired others around him. He was a people person and he never forgot where he came from. He epitomized Pittsburgh — hard working, humble, no-nonsense, tell it the way it is and never forget where he came from. That’s him, that’s Pittsburgh.”

Said Steelers general manager Kevin Colbert, like Rooney a graduate of North Catholic High School, “You could speak all day and never encompass what he means, not only to the Steelers but to this game.

“I just think it’s his sincere interest in people, first and foremost, and his ability to treat everybody fairly but also encompassing a great understanding of our game and in particular the Pittsburgh Steelers.”

Rooney officially succeeded his father as president of the Steelers in 1975, but Art Rooney Sr. gave him control nearly a decade earlier and he quickly reconstructed a franchise that had little success on or off the field since its inception in 1933.

One of his earliest decisions proved among his greatest, when he hired Chuck Noll as coach in 1969 after he first offered it to Joe Paterno, who turned it down. He gave Noll total say of personnel and the draft and stuck with him as he reshaped the roster and shook out the losing doldrums. It paid off in four Super Bowl victories in the 1970s, which ranks near the top of NFL championship dynasties.

Around the time Noll was hired, Rooney also persuaded sports writer Bill Nunn Jr. to join his scouting staff. Nunn would discover many of the players at predominantly small, black colleges who had largely been overlooked during those times and who would help forge that 1970s dynasty.

The 1980s were not as kind to Rooney’s Steelers. Not only did they miss the playoffs in six of those 10 years, but the NFL also lost games to two separate players’ strikes and was challenged by another competing league, the USFL.

Yet, Rooney was prominent in ending both strikes and guided the Steelers through it all. The team emerged in the early 1990s revitalized, with a strong roster and a new coach. Bill Cowher succeeded the retired Noll in 1992, and the Steelers responded by making the playoffs six consecutive years, competing in three AFC championships and their first Super Bowl in 16 years.

There was some sentiment to make him NFL commissioner in 1989 but he quickly put that to rest, preferring to run the Steelers, not the league, which instead hired Paul Tagliabue.

Yet Rooney maintained a powerful influence on the NFL as an owner and as a voice of reason in the league. He was a power-broker and developed close relationships to all three commissioners during his time — Pete Rozelle, Tagliabue and then Roger Goodell, who received word firsthand from Rooney in 2006 that he had just been chosen for the job.

“He speaks to the owners, and they believe what he says,” said Joe Horrigan, a vice president of the Pro Football Hall of Fame. “He brings that legacy feeling of importance of preserving the heritage of the game. It’s a sincere thing on his behalf, and to us it’s an essential ingredient.”

Rooney often piloted his own plane to NFL offices in New York for various issues or committee meetings, many of which he headed, including its most powerful, the NFL management council.

“I’ve been asked why I spend so much time on league matters, that you should take care of your own,” Rooney said. “I always said we’re part of the NFL. By helping them, we’re helping ourselves.”

In addition, he was so respected by the players and their union that the late Gene Upshaw, as longtime NFLPA executive director, often sought his counsel, even traveling to Pittsburgh on occasion to do so, and was praised by Rooney during his Hall of Fame acceptance speech.

“He was deeply involved in resolving disputes and reaching agreements with the NFL Players Association from the 1970s into the present,” Tagliabue wrote in the preface to Rooney’s autobiography, published in 2007. “His integrity and understanding of both football and team economics made him invaluable in negotiations on the college draft, the need for competitive balance on the football field, free agency, and player safety matters.”

Former tackle Tunch Ilkin, the Steelers union player representative at the time, told how, during the bitter 1987 players’ strike, Rooney secretly slipped him a key to the club’s grass practice field on the North Side. His instructions to Ilkin were to “keep the team together” while the NFL proceeded to play a three-game schedule with “replacement” players.

At first, he opposed free agency, which the players sought at the time and ultimately earned in a landmark court case and then collectively bargained with the league in 1993. He thought it would be disastrous for the sport but later came around to embrace it and work to have his team use it and the salary cap largely to its benefit. It was under that new system that the Steelers finally returned to the Super Bowl after the 1995 season and won two more Lombardi trophies after the 2005 and 2008 seasons.

When Rooney was elected into the Pro Football Hall of Fame in 2000, he and his father, Art Rooney Sr., who was inducted in 1964, joined Tim and Wellington Mara of the New York Giants as the only other father-son combo in the Hall of Fame.

“It is special to join him here,” Rooney said of his father in his acceptance speech. “He gave me the understanding of what the league meant. He gave me the commitment to do everything possible to keep it strong and viable.”

Rooney invited Greene, whom he considered the greatest player in Steelers history and a friend, to present him in Canton.

At age 67, Rooney had reached the pinnacle of his profession with that induction at Canton, but he was far from slowing down and ready to embark on new ventures, one that would ensure his franchise remained in Rooney control and another that sent him to a government job overseas.

First, he and his son Art Rooney II helped pave the way for a new stadium, Heinz Field, which replaced Three Rivers Stadium for the 2001 season.

Two years later, Dan turned over the presidency of the team to Art II and became its chairman. That same year, as chairman of the league’s diversity committee, he pushed for the adoption of a rule that would require all NFL teams searching to fill the position of head coach to interview at least one minority candidate. It became known as the “Rooney Rule” and has been cited for an increase in the number of minority head coaches in the league, one of which would be hired by the Steelers four years later.

In 2007, after Bill Cowher’s resignation, Dan and Art II hired the first black head coach in team history, Mike Tomlin, who would guide the Steelers one year later to their sixth Super Bowl win, more than any other NFL team.

That same year, Dan and Art II negotiated some difficult transactions to preserve the family’s control of the Steelers yet at the same time sell portions of the franchise to new partners to abide by NFL rules and to bring fresh money into the organization. They completed the transition in 2009 with a number of new partners investing in the franchise.

The new ownership group that formed remained under the control of Dan and Art II, who combined owned 30 percent of the team as required by the NFL for a majority owner.

Ultimately, all four of his brothers sold nearly all of their stakes in the Steelers, and Art Rooney II became the principal owner.

“I’m a lifelong Steelers fan but also a lifelong Rooney fan,” said Thomas Tull, one of the main partners who came aboard in 2009. “It’s very important to me that the Rooney family is always the head of the Steelers.”

It was important to Dan Rooney too, as it was to his father, who kept the team afloat during the tough times in the depression and during lean years of victories and attendance through the ’50s and ’60s.

“Speaking of accomplishments, if that’s the proper word, I would say keeping the team in Pittsburgh and being as viable as we’ve been,” Dan Rooney said, regarding his personal achievements.

There was another major pursuit Rooney would take well into his 70s.

Like his father, a longtime political junkie, Dan Rooney, who never ran for office, supported many who did. A lifelong registered Republican (also like his father), Rooney nevertheless leaned more in favor of Democrats.

He threw himself into the successful presidential campaign for Barack Obama in 2008, stumping often throughout Western Pennsylvania before the election. Obama appointed Rooney U.S. ambassador to Ireland, his ancestral home, in 2009.

Chicago Bears owner Mike McCaskey said at the time: “To choose a man who has such a long and productive association with Ireland and has actively tried to provide resources to help build unity within the different communities there, I’m just thrilled for Ireland and thrilled for the United States. It’s an inspired choice.”

He served through 2012, often making the round-trip flight home from Dublin to watch the Steelers play.

After his three years as ambassador, Rooney returned to the Steelers as their chairman again, throwing himself back into the daily operations of his beloved franchise.

Besides his devotion to the NFL and Steelers, Rooney contributed to and often headed many charitable works, usually without much fanfare. One of his favorites is the American Ireland Fund, which he and Tony O’Reilly, a former CEO of H.J. Heinz Co., founded and developed into a worldwide fundraiser with three goals: peace, culture and charity.

He had a keen sense of history as well, something highlighted when he planned a unique cross-country trip for his family in the summer of 2003 that followed the Lewis & Clark Trail blazed 200 years earlier, starting in Pittsburgh.

Rooney, born on July 20, 1932, grew up on the North Side with his parents, Art and Kathleen, and his five brothers — Art Jr., Tim and twins Pat and John. He played football at North Catholic High School, where he famously was voted second-team Pittsburgh All-Catholic league quarterback behind one Johnny Unitas of St. Justin’s High.

He graduated from Duquesne University, where he majored in accounting. He quickly went to work for his father with the Steelers. A former ballboy for them, Dan Rooney started out selling ads for the game-day program and immersed himself into many of the business and football activities that would do him well as the Steelers’ future leader.

Rooney and his wife, the former Patricia Reagan, were married in 1952 and had nine children.