John Mark was born and raised in Lexington, South Carolina. After graduating summa cum laude from Clemson University in 2002 with a B.S. in Marketing, he moved to New Orleans to attend law school. In 2005, he graduated from Tulane Law School, magna cum laude. He finished in the top ten law students in his class and was elected to the Order of the Coif. While in law school, John Mark served as a managing editor of the Tulane Law Review. He also founded and served as the president of the Tulane Christian Legal Society.
Following law school, John Mark worked with a New Orleans firm for twelve years in the litigation division, concentrating on trust and estates and commercial fraud litigation. He handled a broad spectrum of complex suits for both plaintiffs and defendants, and earned a partnership with that firm. He appeared in state and federal district courts, as well as appellate courts, throughout Louisiana. John Mark is active in the New Orleans Bar Association, serving as a co-chair of the Business Law Committee. He is also the treasurer of the New Orleans Christian Legal Society, having served in that position since 2011.