Ansel Lothrop White was born on June 26, 1835, in Belfast, Maine, to Robert White and Lois Lothrop. His father was a ship builder who owned $4,000 of real estate and $20,000 of personal property by 1860. His mother died on June 19, 1842, and his father married Eliza Simonton on October 7, 1845. White grew up and attended school in Belfast, Maine.
He enlisted in the Union army on August 25, 1862, and he mustered in as a sergeant in Company D of the 19th Maine Infantry later that day. He was promoted to 2nd lieutenant on November 10, 1862, then to captain on October 31, 1864. The regiment took part in the Battle of Fredericksburg, the Battle of Chancellorsville, the Battle of Gettysburg, the Overland Campaign, the siege of Petersburg, and the Appomattox campaign. He mustered out on May 31, 1865.
White returned to Maine after the war, and he married Mary Alden on November 24, 1869. Their daughter Emily was born around 1872, but she died on February 1, 1880. They moved to Brooklyn, New York, around 1877, and he worked as a merchant there. They returned to Belfast by the early 1900s. His wife’s health deteriorated in the early 1900s, and by 1910, she was a patient at the Eastern Maine Insane Hospital in Bangor, Maine. White was reportedly distraught at his wife’s condition, and he committed suicide near Bangor on June 1, 1910.