William H. Pettes was born on December 24, 1815 in Windsor, Vermont, the son of Frederick Pettes and Harriet Mynderse. He attended West Point, graduating in 1832 as a Brevet 2nd Lieutenant.
Pettes was appointed to the 1st Artillery Regiment, serving at Beaufort, N. C., from 1832‑33, and at Ft. Monroe from 1833-1834. He was promoted to 2nd Lieutenant on September 30 of 1833. In 1834 Pettes was moved to the garrison in Charleston, South Carolina and then took part in the Florida War in 1836, participating in the Defense of Volusia on April 14, 1834 and a skirmish on May 8, 1836.
He resigned on September 11, 1836 and became Asstant Commissioner for the distribution of supplies to destitute Floridians. In 1837 Pettes began work as a civil engineer for the United States government, acting as superintendent of harbor improvements on the Salmon River in New York and on the Genesee River from 1842-1846, at Buffalo, New York from 1853-1855, and at Dunkirk, New York in 1855. He became Superintendent of Construction for the Buffalo Custom House and Post Office from 1855 to 1859, and was working as a civil engineer in the Buffalo area at the start of the Civil War.
On January 3, 1840 Pettes married Ann Sophronia Mansfield. From 1841 to 1850 the couple had three children, Frederick, Anna and Charlotte. Ann died on in Buffalo.
When the war began Pettes was appointed Lieutenant Colonel of the 50th New York Volunteers on September 18, 1861. The 50th served in the Washington Defences and on October 22, 1861 was redesigned the 50th New York Engineers. The 50th New York was stationed at Alexandria until March 18, 1862, when it left with McClellan’s Army of the Potomac for the Virginia Peninsula Campaign.
Pettes’ regiment was involbed in the Siege of Yorktown from April 5 – May 4, 1862, and then in engineer operations on the Chickahominy and James Rivers beginning in June. In September it returned from the Peninsula to the Engineer Depot in Washington, D. C., then spending the next three months repairing roads and wharves at Acquia Creek, Virginia.
Pettes and the 50th took part in the Rappahannock Campaign from March to June of 1863. The regiment skirmished with the enemy while constructing pontoon bridges at Pollock’s Mill on April 29, 1863, at Banks’ Ford on May 3.
Pettes was promoted to colonel of the 50th New York Engineers on June 3, 1863. As the Gettysburg campaign began the regiment constructed bridges at Deep Run on June 5, 1863. After building the bridges that allowed the Army of the Potomac to cross its namesake river on the way to the Battle of Gettysburg the 50th Engineers moved to the Engineer Depot at Washington, D. C., fro July 3 to Sepember 2, 1863.
Pettes and the regiment returned to the field at Rappahannock Station, Va., from Sepember 3 to Oct. 10, 1863, then returned to winter quarters at the Engineer Depot at Washington, D. C., from October 1863, to March 1864. It resumed operations in the field at Rappahannock Station in March and April of 1864. In May of 1864 Pettes was given command of the Engineer Depot in Washington, D. C., supplying the Army of the Potomac with engineer equipment until the end of the war.
He mustered out of service with his regiment on June 14, 1865.
William H. Pettes died on in Fort Washington, Prince George’s County, Maryland.