Art McNally, the first on-field official inducted into the Pro Football Hall of Fame, has died. He was 97.

His son, Tom McNally, said Monday that his father died of natural causes at a hospital in Newtown, Pennsylvania, near his longtime home.

McNally died less than five months after getting inducted into the Hall of Fame following more than a half-century working as an on-field official, the head of officiating for the NFL and an adviser to the league who is credited with modernizing the practice of how games are officiated.

"Art McNally was an extraordinary man, the epitome of integrity and class," NFL commissioner Roger Goodell said in a statement Monday. "Throughout his distinguished officiating career, he earned the eternal respect of the entire football community. Fittingly, he was the first game official enshrined in the Pro Football Hall of Fame in Canton, Ohio. But more importantly, he was a Hall of Fame person in absolutely every way."

While baseball, basketball and hockey had inducted several officials into their Halls of Fame, McNally was the first to receive the honor by the NFL back in August.

There couldn't have been a more appropriate choice for the honor than McNally, whose fingerprints are all over how games are officiated even today.

Art McNally became the first on-field NFL official to be inducted into the Pro Football Hall of Fame in August. AP Photo/David Dermer, File

After a nine-year career on the field, McNally overhauled the department when he took it over in 1968 and remained involved until retiring in 2015.

"Art McNally was a quiet, honest man of integrity," Hall of Fame president Jim Porter said in a statement. "To see Art's decades of service recognized with his enshrinement as part of the Class of 2022 was a special moment for the Hall. His legacy as a strong leader who helped usher in the advanced training of officials and the technology necessary to keep up with a faster and more complicated game will be preserved forever in Canton."

McNally got his start in officiating in an informal way when he called games while serving in the Marines in World War II. He went on to call more than 3,000 games in football, basketball and baseball, chronicling them all in books he kept, according to son-in-law Brian O'Hara.

Before shifting to the NFL league office in 1968, McNally would often officiate high school, college and professional games on the same weekend.

"He was natural at it," O'Hara said this past summer. "From being a teacher and being kind of like a rule follower his life because he followed the rules. ... The biggest thing was he enjoyed making it fair. That's all he wanted to do was to be fair and to get it right. I guess that's the things he enjoyed about officiating."

McNally's biggest impact came in how the NFL evaluated and trained officials in a system that is still mostly in place today.

Under his watch, the NFL standardized how officials worked a game in their positioning and what calls they made to bring more consistency to the sport.

He used All-22 game film to teach the officials and grade their performance, using the film to teach as well as evaluate officials. He utilized weekly training videos and rules quizzes to help improve the officiating across the league.

"That was brand-new," Dean Blandino, one of McNally's successors as the NFL's head of officiating, said before McNally's induction.

"That was kind of cutting-edge. People weren't doing it. Art came in and understood that this was something that was needed and laid that foundation, and that foundation is still what we stand on today in the officiating world. Every league in every sport at every level has an evaluation system and that all goes back to Art."

McNally also helped implement the NFL's first use of instant replay in the 1980s and got his first chance to work a Super Bowl as a replay official following the 1986 season.

That version of replay was abolished in 1991, but McNally provided guidance to his successors when replay returned in 1999, as he was steadfast in his belief that the league should use any tool to help officials make the correct calls.

"You just want to get it right," former NFL referee Ed Hochuli said this summer. "Art was the definition of that. If you look up the definition of integrity in the dictionary and there's a picture of Art."

McNally is survived by his wife, Sharon, his children Marybeth, Tom and Michael, and his grandchildren.