In his early manhood Colonel Leighton was a member of the St. Louis bar, but in later life he was widely known as a manufacturer and public benefactor. Born in Cambridge, Massachusetts, he moved to Cincinnati with his family in 1844. He graduated with honors from Woodward College and immediately began the study of law. After three years’ preparation for the bar, he was admitted to practice in the United States and State courts. Two years later he came to St. Louis, Missouri and had established himself in practice when the Civil War broke out and he became a soldier. An ardent Unionist, he entered the government service commissioned a lieutenant in the Third Missouri Infantry Regiment of the United States Reserve Corps. He was later promoted to major of the Fifth Missouri State Militia Cavalry and still later transferred to the Twelfth Cavalry Regiment. In the fall of 1861 he was assigned to duty as provost marshal of the St. Louis Division. He was later promoted to colonel of the Seventh regiment, Enrolled Missouri Militia, and served in that capacity until the end of the war. After the war, he resumed his law practice in 1865 and became general counsel of the Missouri Pacific Railroad Company, a position he held until 1874. Through this connection he acquired certain railroad interests and was compelled to relinquish his law practice and devoted himself entirely to his business affairs. The Bridge & Beach Manufacturing Company was one of the largest iron manufacturing establishments in the West and Colonel Leighton became president of this corporation. Officially connected with the Union Pacific Railroad Company, the Union Trust Company and the Boatmen’s Bank, he was also involved with Bellefontaine Cemetery, Washington University, the Missouri Historical Society, the Commercial Club of St. Louis, the St. Louis Academy of Science, the St. Louis School of Fine Arts and the St. Louis Medical College. He was one of the founders of the National Arts Club of New York and was one of the trustees and vice-presidents of that organization.In addition to being president of the New England Historical Society and the National Sound-Money League, he was a member of the St. Louis Academy of Science, the American Academy of Political and Social Science and of the American Folklore Society.