Thomas Mercer Girdler graduated from Lehigh in 1901 with a BS in mechanical engineering. His first position in the steel industry was as a heater and blower salesman, but by 1914 he was general manager at Atlantic Steel Company. That year he joined Jones and Laughlin Steel Corporation as its president.
In 1930, he was appointed President and later the first Chairman of Republic Steel. Girdler guided the company through the difficult years of the Depression to emerge as one of the "Big Three" in the steel industry, along with U.S. Steel and Bethlehem Steel. Girdler's management of Republic Steel was recognized as a "one man show," as he acquired new companies and revamped existing plants. One such acquisition was of Consolidated Aircraft and Vultee Division (merged into Convair) which built B-24 bombers and PBY Flying Boats during WWII. He was also served as a vice president of the Iron and Steel Institute for a number of years.
Lehigh awarded Girdler the honorary degree of Eng. D. in 1955. He retired from Republic Steel in 1956 and spent his remaining years raising race horses.
Girdler developed his leadership skills in college where he was not only involved in over twenty clubs, but also served on the executive board for many of them. He took part in music and theater as a first bass in the glee club and choir, stage manager and eventually manager of the Lehigh University Minstrel Association, and stage manager and president of the Mustard and Cheese Drama Club. As far as athletics, he was the manager for the junior baseball team in the Cup Contest, the athletic representative for his class, and president of the Athletic Committee.
Girdler was Assistant Editor-in-Chief for the Epitome and Associate Editor for the Brown and White. He helped to plan the Junior Hop, was in the Sophomore Cotillion Club, and was the chairman of the Calculus Cremation Committee. He managed to make time for his fraternity, Beta Theta Pi, and a number of other clubs: Kappa Kappa, Arcadia, and Sword and Crescent. Girdler also participated in the Students' Honor Court.
Despite his busy schedule, Girdler was a top student earning him the Freshman Wilbur Prize in Math, and a spot in the engineering honor society, Tau Beta Pi. He was also a part of the Mathematical Club and the Mechanical Engineering section of the Engineering Society.