William H. Thompson was born around 1842 in Illinois to Joseph and Emily Thompson. His father was a Presbyterian minister who owned $500 of real estate by 1850. The family moved to White County, Indiana, in the 1840s, and his father died on December 7, 1851. His mother married William McGavern several years later, but McGavern died on December 3, 1858. By the early 1860s, Thompson was living in Lagro, Indiana. His mother later testified that she was “wholly dependent on him for her support.” He paid her rent and provided “all that she required in keeping house such as flour for her living and vegetables.”
He enlisted in the Union army in June 1861, and he mustered in as a private in Company F of the 17th Indiana Infantry. The regiment took part in the siege of Corinth and the Battle of Chickamauga. He eventually earned a promotion to sergeant. He was wounded in the right thigh on November 27, 1863, and he died near Cleveland, Tennessee, on December 4, 1863.