The history of Hartford is actually an account of two communities. The older settlement to take the name Hartford dates to before the Civil War. About seventeen families were homesteading in southern Sebastian County, between the Sugar Loaf and Poteau mountains. Their settlement was known to some residents as the Old Sugarloaf Valley Community, but most called the settlement Hart's Ford, honoring Betsy Hart, the widow of James Hart, who lived near the crossing of West Creek. A post office was established in Hartford in 1874. By 1891, the community included a union church (shared by Methodists, Cumberland Presbyterians, and Baptists), a public school, and a store. Meanwhile, a second settlement a few miles away developed after the Civil War. Sometimes called Center Point, it later took the name Gwyn from landowner Wylie P. Gwyn (or Gwynn), who began homesteading in a log cabin in 1868 and who began mining coal on his property sometime in the 1880s. Late in that decade, the Choctaw-Memphis Railroad Company bought a right-of-way near Gwyn. In 1899, the railroad purchased additional land that was known to contain coal deposits. The company was later acquired by the Rock Island Railroad.

The new community that grew up along the railroad was variously called Gwyn and New Hartford, while the older settlement was known as both Old Hartford and West Hartford. The newer community was incorporated early in 1900. By 1905, it was using the name Hartford.