Manufacturer and financier. Arriving in the United States when he was 23 years old, Allen came to St. Louis and worked as a contractor and builder. His intense energy soon gave him a good start on the road to fortune and within a few years he became the owner of two sawmills, one of which was located in St. Louis and other on the Gasconade River. After manufacturing lumber for a time he disposed of his sawmills and invested his capital in the iron business, becoming a member of the well-known and prosperous firm of Gaty, McCune and Company. He was a member of this firm until 1855, when he withdrew to establish the Fulton Iron Works. This business grew to very large proportions under his management and was passed on to his son. Mr. Allen helped to establish various corporations and was connected with many such institutions in an official capacity. He was elected president of the Covenant Mutual Life Insurance Company of St. Louis in 1853, and in 1857 he and other well-known businessmen organized the Hope Mutual Fire Insurance Company, of which he was director for many years. He was also a director of the Bank of the State of Missouri, vice-president of the O'Fallon Polytechnic Institute, and vice-president of the North Missouri Railroad at one time. During the golden age of steamboating on the Mississippi and Missouri Rivers he was interested in various steamboats and was a director of the St. Louis & Vicksburg Anchor Line Company, and also of the New Orleans Anchor Line Company.

Interested for many years in the "Missouri Republican" newspaper, later known as the St. Louis "Republic," he was one of the influential factors in directing its policy and influencing public sentiment through that channel.

Married twice, he was survived by four children. He married Frances W. Adams on December 10, 1846 in St. Louis, Missouri and later married Eugenia L. Paschall Carr on July 13, 1871 in St Louis, Missouri.