Thomas Edward Whelan was born April 15, 1895, at St. Thomas, North Dakota, and graduated from high school there. He attended the University of North Dakota at Grand Forks, and was basketball manager and assistant advertising manager for the Dacotah. He was also involved in Sock and Buskin, Phi Delta Phi, and Sigma Chi. He graduated with a Bachelor of Law degree in June 1916.

He served in World War I, entering the United States Army in Cavalier, North Dakota on July 22, 1918. He was discharged on November 26, 1918. After his discharge, he farmed at St. Thomas with his brother. He married Mabel Stewart on February 3, 1927.

Whelan, a Republican, served as a state senator from 1932 to 1940, and then was a candidate for the Republican nomination for U.S. Senator, opposing then senior North Dakota Sen. William Langer. From 1938 to 1940, he was a member of the Republican program committee and helped to map the farm plan which was adopted by the party. He was Republican state chairman from 1940 to 1948.

In 1951, President Harry Truman nominated Whelan to be the United States Ambassador to Nicaragua. He served in this position from 1951 to 1961. When President Dwight Eisenhower took office in 1953, he submitted his resignation, but was reappointed to the position. He was the first North Dakotan to serve as an ambassador.

He also was active in the American Legion, serving as state commander for a time and for several years as national chairman of the American Legion Foreign Affairs Committee.

Thomas Whelan died August 31, 1977 at Grand Forks. He is buried at St. Thomas Catholic Calvary Cemetery in St. Thomas.