O'Laughlen was one of John Wilkes Booth's earliest friends as the Booth family lived across the street from the O'Laughlens. O'Laughlen learned the trade of manufacturing ornamental plaster work. He also learned the art of engraving. At the outbreak of the Civil War O'Laughlen joined the Confederate Army but was discharged in June 1862. He returned to Baltimore and joined his brother in the feed and produce business.