Pvt Smallwood enlisted into the US Army at Cincinnati, OH on December 18, 1874. He was described as 5'-8" tall, brown eyes, brown hair and a dark complexion. His civilian occupation was farmer.

On February 8, 1875, Private William Smallwood was assigned to Company E, 7th US Cavalry at Opelika AL. The 7th Cavalry was performing constabulary duty at the time, which it did for 18 months in the deep South. Company E was commanded by a Lt. Algernon Smith and was known as the Gray Horse Troop, because of the gray horses they rode.

At the Battle of the Little Bighorn, Company E was attached to Custer's Battalion of five companies, C, E, F, I and L. William was killed during the fighting, and his remains were not identified. It is likely that his body was first buried where it was found on the battlefield. William was said by one source to be a popular fellow, and the written account states that when friends from the other companies came upon the site of the battle, they found one man of the right stature, build, and complexion who they determined to probably be William near the deep ravine, even though the bodies were in a state of decomposition. Company E had made a fighting advance off of "last stand hill" towards the river, and were cut down along the way.

Lakota and Cheyenne warrior accounts report that Company E fought in a well organized manner, until overwhelmed by the superior numbers of attacking warriors.

In 1881 all known battlefield burials were moved to a mass grave on Last Stand Hill.

The following From Richard L. Smallwood-Roberts:

William Smallwood was born 1854-1855 to David R. Smallwood and Catherine Garrett in Vernon, Jackson County, Indiana, about 10 miles to the East of Jonesville. One of four children. His enlistment record says that he was 22 years old in 1876 when he died, not when he enlisted. Note that the record is postmortem and details his death if he didn't just lie about his age at enlistment. Army records are like that. He was five years old in 1860. He wasn't born in Jonesville, he was born in Vernon Township, about 10 miles to the Southeast. He was just working there when he enlisted. He started working other farms at age 13. My cousins were the only Smallwoods living in that area at the time. There were cousins of mine in Bartholomew County, but they never had a son William. William was my fifth cousin, twice removed. Our common ancestor was my Great x 6 Grandfather, James Smallwood Jr., son of Colonel James Smallwood (French and Indian Wars).