William Sidney "Sid" Hatfield (May 15, 1891 or 1893 – August 1, 1921), was Police Chief of Matewan, West Virginia during the Battle of Matewan, a shootout that followed a series of evictions carried out by detectives from the Baldwin-Felts Detective Agency.
Hatfield was born in Blackberry, Pike County, Kentucky, the tenth of twelve children (of whom nine survived infancy) of Jacob Hatfield (c. 1843/45 – 1923), a tenant farmer, and his wife Rebecca Crabtree (b. circa 1856). His grandfather, Jeremiah Hatfield, was a half-brother to Valentine Hatfield (1789–1867), grandfather of William Anderson "Devil Anse" Hatfield, leader of the Hatfield family involved in the famous Hatfield-McCoy Feud (see Hatfield Family Tree). According to the 1900 Census, two older brothers, Orison and Hereford, an older sister Chloe, and a younger sister and brother, Martha Alice and Freeland, were then still living at home with him and their parents. His eldest sister Vandalia or Vandella was already married by this time, and an older brother, Melvin, had left home.
As a child, Hatfield worked on his father's farm. He became a miner in his teens, and then worked as a blacksmith for several years. He received his nickname, "Smilin' Sid", because of the gold caps on several of his upper teeth. He seems to have had a reputation for hard living and fighting, and his appointment in 1919 to the post of Police Chief of Matewan, by the mayor, Cabell Cornelis Testerman (1882–1920), surprised some of the more 'respectable' townsfolk. However, he was a staunch supporter of the United Mine Workers of America, as was Testerman: together, they were instrumental in leading the mining community's resistance to the Baldwin-Felts operatives. Operatives offered both men substantial bribes to allow them to station machine guns in the town. Hatfield and Testerman refused. The Battle of Matewan was precipitated by the Baldwin-Felts agents' attempts to evict the families of unionized miners.
On June 2, 1920, in Huntington, he married Jessie Lee Maynard (1894–1976), the widowed second wife of Testerman, who had been mortally wounded in the battle. The speed of the marriage led to an attempt at arrest and accusations by Thomas Felts and the Baldwin-Felts spy, Charles Everett Lively, that he, not Albert Felts, had shot the Mayor because of his desire for Jessie. However, according to Jessie, her first husband, aware of the danger of their situation, had asked that his friend take care of her and their young son, Jackson (1915–2001), should he be killed.