Imus died Friday at a hospital in College Station, Texas, after being admitted on Christmas Eve. A cause of death is unknown at this time.

The cowboy hat-wearing shock jock's death comes less than 2 years after he retired. His final day on the "Imus in the Morning" radio program was March 29, 2018. Don made the announcement of his retirement via Twitter in January 2018, saying ... "Turn out the lights...the party's over."

Imus hosted his radio show for almost 50 years, and was inducted into the National Radio Hall of Fame in 1989.

His radio career began in the late '60s, and he started his morning show in 1971 at WNBC in New York City. Over the years, he became popular for pushing boundaries on the air ... but was also known for making comments considered racist, misogynistic and xenophobic.

Because of that, Don faced many lawsuits and accusations of defamatory speech, and had a well-known rivalry with fellow "shock jock" Howard Stern.

In 2007, Imus made headlines for his offensive remarks about the Rutgers Women's Basketball team, who he referred to as "nappy-headed 'hos" and "jigaboos."

He was fired by CBS shortly afterward, but made a return to radio and TV later that year.

Don was also a successful stand-up comedian, who led an admittedly wild lifestyle and battled alcoholism and a cocaine addiction. He went to rehab in 1987, and suffered many health setbacks afterward ... including a collapsed lung in 1992 and a nasty fall from a horse in 2000.

He revealed to his audience in 2009 he had been diagnosed with prostate cancer.

Don and his wife did a lot of charitable work, including founding the Imus Ranch in 1999 ... an organization that helps kids affected by cancer and blood disease. The ranch closed, however, in 2014.

Imus is survived by his wife of 25 years, Deirdre, sons Wyatt and Lt. Zachary Don Cates and daughters Nadine, Ashley, Elizabeth and Toni.

He was 79.