born , Feb. 10, 1808, Springfield Township, Pa., U.S.
died May 27, 1874, Philadelphia, Pa.
U.S. civil engineer and railroad executive.
He joined the Pennsylvania engineer corps at age 19. In 1847 he was hired as chief engineer of the newly incorporated Pennsylvania Railroad Co., which aimed to compete with trade lines to the west originating in New York and other eastern states. He became its president in 1852 and oversaw construction of a railway that crossed the Alleghenies without using inclined grades. Over the next 22 years, Thomson consolidated a network of lines from Philadelphia to Chicago, expanding the company's track from 250 to 6,000 mi (400–10,000 km).