Calhoun Thomas was born in Beaufort to William Joseph and Tennessee Calhoun Thomas. He attended the University of South Carolina, receiving an A.B. degree in 1924 and an LL.B. in 1926. He practiced with his father and later with his son, in the firm of Thomas and Thomas.
In 1928, he began 20 years of service in the South Carolina House of Representatives. He was Judiciary Chairman for fourteen years and House Rules Chairman for ten years. He also served a number of years as County Attorney.
In 1937, he organized the First Federal Savings and Loan Association of Beaufort and served as President, Manager, Director and Attorney of that organization.
He was a leader in organizing the local United Fund, U.S.O., Rotary and Beaufort County Memorial Hospital. He was President of the Community Club, the Beaufort Gazette Corporation, and the University of South Carolian Alumni Association. He was a Charter member of the Chair Fund of the University of South Carolina Educational Foundation. He was Chairman of the Beaufort County Democratic Party for 20 years.
He married Thelma Penland and they had one daughter, Isabelle, and one son, Calhoun, Jr. He was a member of the Carteret Street Methodist Church and a lifetime grower of camellias, which he shared with his many friends.
Firm, but fair, his word was his bond. He served Beaufort County with an undying devotion.