William was born on the 28th of October, 1881 in Richmond, Virginia, and went on to attend and graduate from the Virginia Military Institute in 1902. He received his commission as a second lieutenant in the Marine Corps on the 1st of February 1904 and went on to serve on several vessels of the Navy all over the world. William had duty stations in Cuba, Panama, the Philippines, and China, and in August of 1915, he took command the 15th Company in Haiti. It was his actions on the 24th of October, 1915, that would earn him the Medal of Honor. The citation reads:

In company with members of the Fifteenth Company of Marines all mounted, Captain Upshur left Fort Liberte, Haiti, for a 6-day reconnaissance. After dark on the evening of 24 October 1915, while crossing the river in a deep ravine, the detachments was suddenly fired upon form three sides by about 400 Cacos concealed in bushes about 100 yards from the fort. The Marine detachment fought its way forward to a good position, which it maintained during the night, although subjected to a continuous fire from the Cacos. At daybreak, Captain Upshur, in command of the three squads which advanced in three different directions, led his men forward, surprising and scattering the Cacos, and aiding the capture of Fort Dipitie.

When the US entered World War 1, William was in command of the American Military Prison and the American Guard Camp. He later returned to Haiti in 1922 with the 1st Brigade for two years and his final duty was as the Commanding General of the Department of the Pacific in San Francisco. While on an inspection tour of his command in Alaska and Hawaii, the airplane crashed and William Peterkin Upshur died on the 21st of July, 1943 at the age of 61. Originally buried in Alaska, he was removed and reinterred at the US Naval Academy in Annapolis, Maryland; lot 250-A.