b. June 9, 1829, in Wilson County, Tennessee; d. January 29, 1901, in Hot Springs, Arkansas. Allen came to Illinois as an infant with his family. In 1849, he graduated from law school in Louisville, Kentucky. He opened a law office in Metropolis, Illinois. In 1853, he moved to Marion in Williamson County and continued to practice law until 1854, when he was elected to the lower house of the state legislature. In 1855, Allen was appointed a United States district attorney; he resigned four years later to practice law in Marion. When his father died in 1859, Allen replaced him as judge of the Twenty-Sixth Judicial Circuit, and he held that office until December of 1861, when he was elected as a member of the Illinois constitutional convention. In the spring of 1862, Allen successfully ran for a seat in the U.S. House of Representatives and held that position until 1865. Allen was a member of the Illinois constitutional convention of 1870. In 1886, he moved to Springfield and became a member of the law firm of C. C. Brown & Son. Allen became judge of the United States Circuit Court for the Southern District of Illinois in 1887.