David Washington Thomas was born on March 26, 1839, in Ohio to Michael Thomas and Charlotte Shippey. His father was a farmer who owned $3,000 of real estate and $600 of personal property by 1860. His mother died on February 27, 1846, and his father remarried soon afterward. The family moved to Cedar Creek, Indiana, in the 1840s, and by 1860, Thomas was working as a teacher.
Thomas enlisted in the Union army on May 15, 1861, and he mustered in as a private in Company G of the 12th Indiana Infantry later that day. He mustered out on May 19, 1862. He rejoined the Union army soon afterward, mustering in as a sergeant in Company E of the 55th Indiana Infantry on June 11, 1862. He mustered out again on September 1, 1862.
Thomas returned to Indiana after leaving the army, and he married Anna Beechgood on August 15, 1872. They had at least two children: Paula, born around 1876; and Frost, born around 1882. Their daughter Paula was born around 1877. He resumed his work as a teacher, and he served as principal of public schools in Bluffton, Indiana, from 1872 until 1873. He became superintendent of public schools in Wabash, Indiana, in 1873 and held the position until 1886. He then became superintendent of city schools in Elkhart, Indiana. He applied for a federal pension in July 1904 and eventually secured one. He retired in 1906, and he died of “angina pectoris” in Elkhart on March 20, 1915.