During his tenure as president, he helped create BusinessWeek magazine in 1929, the same year that McGraw-Hill stock was publicly traded for the first time.
He was responsible for changing the four-year-old News-Week magazine's name to Newsweek and introducing international editions.
He was named honorary chairman of the board when the Washington Post Company bought the magazine in 1961.
Sarah Lucille Turner, who had been one of the first women elected to the Missouri House of Representatives, became Muir's secretary while he was president of McGraw-Hill.
After a hiatus she returned to work for him at Newsweek, eventually becoming the magazine's personnel director.