William Allen was born in Edenton, North Carolina, and moved to Chillicothe, Ohio, where he attended Chillicothe Academy and studied law. He was admitted to the bar in Ohio at age 21 and later served as a United States Representative from Ohio. Allen spent a significant portion of his career in the public sector, where he was known for his pro-slavery stance and vocal opposition to President Abraham Lincoln during the Civil War. After retiring, he was honored with a statue in the National Statuary Hall Collection, which was later replaced due to his controversial views.

William Allen's political identity is marked by his staunch pro-slavery stance, which sharply contrasts with his representation of Ohio. His vocal criticism of President Abraham Lincoln during the Civil War further underscores a rigid ideological positioning that alienated many contemporaries. Allen's legislative record reveals an unexpected convergence with opposing factions on certain issues, suggesting a highly calculated approach to regional interests. Despite his controversial legacy, Allen's influence is still commemorated, albeit in a diminished capacity, with a relocated statue.