Colonel Fitzhugh was born May 8, 1818 in Kentucky, but was raised in Missouri. As a teenager, Fitzhugh joined the United States Army, and served in the Second Seminole War. In that war, he fought under future President Zachary Taylor at the battle of Lake Okeechobee, Florida. Later, Fitzhugh participated in the Mormon Campaign in Missouri, which drove the newly-founded Mormons west toward Utah. By the 1840s, the Fitzhugh family had moved to Collin County, where William married Mary Jane Rattan on September 24, 1847. Mary Rattan was the sister of Ann Rattan, the wife of Texas Governor James Webb Throckmorton, making him William Fitzhugh's brother-in-law.
William Fitzhugh joined the Texas Rangers at some point during this period, and served in the Mexican-American War alongside legendary Texas Ranger John Coffee Hays. Fitzhugh spent a number of years on frontier defense while in the Rangers, and was even the Captain of a Ranger Company. Fort Fitzhugh near Gainesville, Texas, is named for him, and was one of the outposts for his company. The town of Gainesville also owes its name to him. When names for the town were being proposed, Fitzhugh put forward the name "Gainesville" in honor of his former Commanding Officer, Edmund Pendleton Gaines.
In 1861, Fitzhugh's younger brother, Gabriel, was killed fighting pro-Union Indians in Oklahoma. The young man's body was sealed in a special coffin, and buried in what is now Fitzhugh Cemetery in Collin County.
The following Spring, William Fitzhugh began recruiting for a cavalry regiment to enter Confederate service. Ten companies were recruited from three counties, and on March 10, 1862, Fitzhugh was elected Colonel Commanding in the town square of McKinney, Texas. Fitzhugh was wounded in the arm at Cotton Plant, Arkansas on July 7, 1862, when a Yankee bullet struck his hand and traveled up his arm. The wound did not heal properly, and left the limb crooked for the remainder of his days.
Following the Civil War, Fitzhugh found his home the scene of a shootout when two men involved in the Lee-Peacock feud took refuge on his property, and were chased down by a posse. In 1875, Fitzhugh served as the Doorkeeper of the Texas Constitutional Convention. A composite photo of the delegates to the convention shows Fitzhugh at bottom center. Fitzhugh also served as the Doorkeeper to the Texas Legislature for several sessions. Still serving in that capacity on October 23, 1883, Fitzhugh had returned to Collin County during a break, and was returning to his home from business in McKinney with a friend. As his wagon approached a railroad bridge, the horses took fright, and bolted. Both men were thrown from the wagon, and Fitzhugh was dashed against a nearby rail. He died of his injuries within a few hours. Initially buried in Pecan Grove Cemetery near McKinney, Fitzhugh's body was later exhumed and re interred in Fairview Cemetery near Denison.

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