William Patrick Martin was born on March 20, 1821, in County Cavan, Ireland. He eventually immigrated to America, and he enlisted in the United States army in March 1839. He served in the Mexican American War, and he reportedly performed “gallant service…until disabled by the loss of a leg.” By 1855, he was serving as an ordnance sergeant. He married Margaret Scott, and he had at least three children: James, born around 1846; Margaret, born around 1850; and Asher, born around 1858. The family lived in Groton, Connecticut.
In August 1861, he received a commission as a 1st lieutenant in the 3rd Rhode Island Heavy Artillery. He served as a regimental quartermaster. In August 1862, he was promoted to captain in the commissary department.
He remained in the army after the war, and he eventually earned a promotion to captain in the Regular Army. He retired on March 20, 1885, and settled in Providence, Rhode Island. He died on March 19, 1886, in Washington, D.C.