Colonel William Henry Boyle was a professional soldier who served in the Civil War and was stationed in the Pacific Northwest from 1866 to 1884, serving in the Modoc War, 1872-1873. Boyle entered the service of the New York Volunteer Artillery on January 19, 1862 and quickly rose to the rank of first lieutenant. He served under Generals Crook and Sheridan, receiving commendations from both. He fought at Harper's Ferry, Lynchburgh, and Cedar Creek.

Boyle's service in the regular Army began when he reenlisted in May, 1866, entering the infantry with the rank of second lieutenant. In 1869 he was sent west to the Umatilla Indian Agency in Oregon to act as agent, a post he held until 1871. He was sent to engage the Apaches in Arizona in 1872 but returned to the Department of the Columbia to act as Adjutant and Field Quartermaster to the troops in the field during the Modoc War, from 1872 to 1873. In 1877 he commanded Fort Lapwai, in Idaho, and arranged for council with Chief Joseph in hopes of preventing war with the Nez Perce Indians. He remained in the Pacific Northwest, in conflict with the Bannocks and Paiutes, until June of 1884. His new command found him on the plains at Fort Sidney in Nebraska and Fort Randall in South Dakota.

In 1883, at the time of his advancement to captaincy, the Army began efforts to ascertain Boyle's true date of birth (DOB) and correct age. By 1895 the matter was still unresolved, and his DOB ranged from 1832 to 1838.

An engraved loving cup, given to him by grateful students, places Colonel Boyle at Marmaduke Military Academy in Maryland, in 1906, having retired from active service in 1900. A 1913 listing of the status of Army officers who served in the Civil War shows Col. W. H. Boyle retired and his age still in dispute, calculating his DOB as 1836; a 1914 edition calculates it to 1832. Both listings have the designation "D" (dead) penciled in the margin next to his name.