CHAPEL HILL — William Friday, a North Carolina icon and retired president of the University of North Carolina system, was in critical condition Wednesday at UNC Hospitals.

A UNC spokesman confirmed the hospitalization, but no further details were available about the health of Friday, who is 91.

In 2008, Friday suffered a minor heart attack, and in 2009, he had surgery to replace a heart valve. But generally, Friday kept a remarkably busy schedule deep into his retirement. He last taped his weekly UNC-TV interview show, “North Carolina People,” on May 9, as he has done since 1971.

On Sunday, he and his wife, Ida, celebrated their 70th wedding anniversary.

Friday is widely known as an esteemed leader in higher education nationally and one of the most revered figures in North Carolina.

Before retiring in 1986, Friday served three decades at the helm of the UNC system during a period of rapid change and growth. On his watch, the university system expanded from three campuses to six and finally to 16. Enrollment jumped from nearly 15,000 students to 125,500, and the annual budget swelled from $40.7 million to $1.5 billion.

He was instrumental in the creation of the Atlantic Coast Conference for athletics and the development of Research Triangle Park. He became a critic of the influence of big money on college sports as a co-founder of the Knight Commission on Intercollegiate Athletics.

A staunch believer in the power of education to lift people from poverty and make them good citizens, Friday was a crusader for state support for universities and making them affordable for families.

In a 2010 interview with The News & Observer to mark his 90th birthday, Friday said the cost of college is a major issue for UNC students of today. “The strength of this place has been that every child in North Carolina could dream of going to one of these institutions, if they did their work,” he said. “Now, the cost is eroding that dramatically.”