Allen was born Allen Macon Bolling August 4, 1816 in Indiana. He grew up a free man and learned to read and write on his own. In the early 1840s, he moved to Portland, Maine where he earned his license to practice law. However, because White people were unwilling to have a Black man represent them in court, in 1845 Allen moved to Boston, Massachusetts. Allen passed the Massachusetts bar exam that same year and he and Robert Morris, Jr. opened the first Black law office in the U. S. In 1848, Allen passed another exam to become Justice of the Peace for Middlesex County. After the Civil War, Allen moved to Charleston, South Carolina and in 1873 was appointed Judge in the Inferior Court of Charleston. The next year, he was elected Judge Probate for Charleston County. Later, Allen moved to Washington, D. C. where he worked as an attorney for the Land and Improvement Association. Allen practiced law right up until his death June 11, 1894.