William N. Walker was born around 1831 in Tennessee to George and Martha Walker. He moved to Indiana sometime before the war. He enlisted in the Union army on July 17, 1861, and mustered in as a 2nd lieutenant in Company E of the 25th Indiana Infantry on August 19. He was promoted to captain on October 23, 1861. The regiment took part in the Battle of Fort Donelson, the Battle of Shiloh, the Siege of Corinth, and the Atlanta Campaign. An Indiana editor praised him as a “gallant soldier” and a “brave Captain,” noting that he was “in the hottest of the fight at Fort Donelson.”
Walker resigned on January 23, 1864, and returned to Indiana. He married Margaret Christian in Dubois County, Indiana, on November 2, 1866, and their son George was born around 1868. Walker worked as a doctor, and by 1870, he owned $800 of personal property. He moved to Logansburg, Illinois, sometime in the 1870s, and he applied for a federal pension in November 1875. He died in Logansburg on March 7, 1876.