Douglas Putnam's grandfather was the famous Israel Putnam, an American army officer and general, who fought at the Battle of Bunker Hill during the American Revolutionary War. Putnam's father, Douglas Putnam Senior, resided in Harmar, Ohio, which at that time was the western part of the town of Marietta. Putnam Senior married Mary Ann Hildreth in the early 1820s, with their marriage producing five children. Samuel and Benjamin Putnam were Douglas' older brothers. His two sisters were Catherine Hildreth, and Elizabeth Perkins Putnam.
During the winter of 1861–1862 Putnam was stationed in Cairo, Illinois. As Paymaster he worked in an office on the same floor connecting with the office of Ulysses S. Grant, where he first met him when he was then a brigadier general. While in Cairo he also met and came to know John Rawlins who was a captain, along with Colonels John McClernand and Lew Wallace and other Civil War notables. Here Putnam also became a good friend and companion of Major Hoyt Sherman, the younger brother of William T. Sherman. The two brothers up to that point had not seen each other in eleven years; Putnam witnessed and wrote about their reunion. In 1861 Putnam entered the volunteer army and served as Paymaster's clerk. That year he organized the Ninety-Second Ohio Volunteer Infantry, which he commanded during the Chattanooga campaign while serving as Adjutant. In the days before the Battle of Shiloh in 1862 Putnam was still a Paymaster, and distributed pay to the soldiers as they arrived at Pittsburg Landing on the Tennessee River, up until April 5, the day before the fighting began. When the battle commenced Putman boarded a steam boat and was then invited by General Grant to join him on the field as his aide. He was present and heard General Grant instruct Captain Baxter to set out and find General Wallace, who was expected to be present, and to relay verbal orders to Wallace to bring his division up. This is when Wallace declined the orders insisting that they be written, resulting in his division being absent during battle. Controversy exists as to whether this allowed the Confederates to prevail resulting in a Union retreat on the first day of the battle. That evening, after the battle and the costly Union retreat, Putnam claims that Grant had remained "cool and collected as if all were going as he had planned". Putnam also fought in the Battle of Missionary Ridge under General Ulysses S. Grant. As part of Brigadier General John B. Turchin's brigade, Putnam led the 92nd Regiment Ohio Volunteer Infantry up the steep slope of the ridge, but while cheering his men forward, was severely wounded as he neared the summit. Putnam would later publish an eyewitness account of the Battle of Shiloh, entitled Reminiscences of the Battle of Shiloh, published in 1890. In the narrative Putnam always referred to himself as "the writer".
Domestic life
In 1869 Putnam moved to Ashland, Kentucky and started up a railroad business, the Lexington and Big Sandy Railroad Co., which later became the Ashland Iron & Mining Co., the latter of which he was president. He also became president of the Ashland Coal & Iron Railway until 1900 when he retired. His two sons, L. R. Putnam and D. G. Putnam were general manager of the Ashland Steel company and president of the Ohio Valley Milling & Supply Co. respectively, both located in Ashland. Putnam also served as a member of the Ashland City Council, and the Ashland School Board, and was active in advancing history course in Ashland's public schools. Putnam was an active member of the Loyal Legion, an organization of Officers of the Civil War. He attended the First Presbyterian Church in Ashland, which he supported for almost fifty years. Douglas Putnam died in his Ashland, Kentucky home, at the age of 79.