Glenn Frey of the Eagles performs in Phoenix in 2010. The Eagles co-founder died Monday in New York after battling multiple ailments. He was 67. The band's music helped define the sound of the 1970s.

NEW YORK — As the Eagles co-founder, singer and songwriter Glenn Frey mastered the mix of rock and country and the band’s hits helped define the 1970s.

Frey died Monday of complications from rheumatoid arthritis, acute ulcerative colitis and pneumonia in New York at 67. He was born in Detroit and formed the band with Don Henley in 1971 in Los Angeles. Frey and Henley came from humble beginnings after playing backup to Linda Ronstadt and later forming the Eagles.

The band released some of the most popular songs of the 1970s: “Take It Easy,” written by Frey and Jackson Browne, and “Hotel California.”

“Hotel California” was just one of the Eagles’ tunes to peak atop the Billboard Hot 100 chart: “Heartache Tonight,” “New Kid In Town,” “One of These Nights” and “Best of My Love” also hit No. 1.

Frey and Henley wrote most of their hits and were known as one of the top songwriting teams. Two of their albums would go on to rank among the top-selling albums ever released: “Eagles, Their Greatest Hits (1971-1975)” and 1976’s “Hotel California” each sold more than 20 million copies. The Eagles were the best-selling American group of all-time.

The band, however, called it quits in 1980 in dramatic fashion at a political fundraiser as threats were exchanged between members during a show.

Frey recorded solo albums and had hits with “You Belong to the City” and “The Heat Is On.”

But 14 years after the 1980 breakup, the Eagles were back, and they launched their “Hell Freezes Over” tour, named after the band famously said it wouldn’t reunite “until hell freezes over.” In 1998, the Eagles were inducted into the Rock Hall of Fame.

Henley said Frey was like a brother to him and the bond they forged was never broken, even in all the tumult.