Civil War historian Bob O'Connor has written a biography of James E. Hanger, who lost his leg in a battle in 1861 and invented a new type of prosthesis to replace his leg. Hanger's prosthesis hinged at the knee and ankle and replaced the peg leg that was previously the most common option then for leg amputees. He later founded J.E. Hanger Co. to manufacture the device. Hanger now has 740 clinics and more than 4,300 employees. "Hanger was the Henry Ford of his time," O'Connor said.