McCain married the former Minnie Leicester Lenz on October 3, 1931, and they were parents of three children: William D., Jr., John W., and Patricia.

[1][3] As part of his military interest, McCain later very strongly promoted a large ROTC at the University of Southern Mississippi when he was president there.

He was a founding member of the Society of American Archivists and wrote several genealogical volumes, including histories of the McCain, Fox, Shaw, and Vance families.

[3][2] In addition, he wrote The Story of Jackson: A History of the Capital of Mississippi 1821-1851 (1953) and The United States and the Republic of Panama (1937).

"[9] The library at the national headquarters in Columbia, TN, is named is his honor,[10] and the grounds are referred to as "MAJ GEN WILLIAM D MCCAIN HQ CAMP.

Once, when testifying in a criminal proceeding in which one of his deans was charged with embezzlement, he was fined $500 and given a thirty-day suspended sentence for threatening to "beat the prosecutor's damned brains out.

In a well publicized speech to a Hattiesburg civic club on March 15, 1969, he lashed out at the state legislature for being so paralyzed by the integration issue that they were causing higher education in Mississippi to "come to a grinding halt.

In the early 1960s he obtained the support of fellow segregationist Governor Ross Barnett to elevate MSC to university status.

As a leader of the pro-segregationist White Citizens' Council and a member of its speakers bureau, he made numerous trips north to present the pro-segregation case.

[8] In a period when pressure was growing nationally to integrate the state's institutions of higher learning, he was well known to vehemently oppose the prospect of having any black students at Mississippi Southern.

[17] On September 15, 1959, Kennard was falsely arrested by constables Charlie Ward and Lee Daniel for reckless driving upon returning to his car from a meeting with President McCain.

[3] After he was jailed, Lee and Daniels perjured themselves before racist Justice of the Peace T. C. Hobby, claiming to have found five half pints of whiskey, along with other liquor.

He closely echoed conservative Republican presidential candidate Barry Goldwater, who heavily carried the Mississippi white vote in 1964.

He blamed Soviet leader Nikita Khrushchev, Communist China, and Fidel Castro for fomenting the civil rights movement in general and particularly the move to integrate public education in Mississippi.

University of Southern Mississippi leaders, such as President McCain, had come to realize that the battle to maintain segregation was lost.

The campus police department had very strict orders to prevent or quickly stop any incident involving the two black students.

Student athletic, fraternity, and political leaders were recruited to keep the calm and protect the university from such bad publicity as Ole Miss had suffered from its reaction to James Meredith.

Preparing for a protracted process of negotiations, McCain asked the black students to elect a leadership group with which he would deal.

[1] In the later decades of his life McCain was best known for his work in successfully—if highhandedly—building a small teachers college into the regional educational powerhouse that became the University of Southern Mississippi and for his anti-integration activities in the 1950s and 1960s.

He was also recognized regionally as an author, lecturer, historian on the Confederacy and post-Civil War period, archivist and genealogist.