John Hart, pioneer of Red River County and early Fannin County sheriff, was born in North Carolina or Virginia in 1790, the son of Josiah Hart. He lived in Virginia and Indiana, and in the early 1820s traveled to Fort Smith, a garrison in Arkansas Territory. He spent the 1820s working as a trapper and trader. He may have cultivated land near Washita Bend in what is now Grayson County, Texas, before 1826. Sometime in the 1830s he led a trapping party down the Washita River into Indian Territory. The party was attacked by Indians; in their retreat they left Hart behind with an Indian guide, and during another attack the guide was killed. Hart, however, managed to escape and canoe to Jonesboro and on to New Orleans.
In 1832 he once again traveled to Jonesboro, where he opened a store and built a house. On July 20, 1836, he enlisted in a volunteer unit of the Texas army from Red River County and was elected captain. After his discharge on October 26, 1836, he moved to Warren, a pioneer settlement that was then in Fannin County. In 1837 he became sheriff of the county. On April 27, 1840, Hart was elected foreman of the grand jury. In 1838 he was awarded a headright for a league and a labor of land. Also in 1838 he served with a volunteer company in campaigns against Indians. For his 1836 service in the Texas army he was awarded 320 acres, of which 120 acres was patented in Fannin County on November 29, 1839. The other 200 acres was patented in Hunt County in 1852 by his heirs. In October 1838 Hart listed for tax purposes $800 in plantation stores, and in 1840 he listed 8,201 acres of land and six workhorses, for which he paid fifty-four dollars tax, the second highest tax in Fannin County. In the fall of 1838 Hart and two partners cleared and fenced seventeen acres and built three cabins in Fannin County. The partnership was dissolved in 1839, and Hart received the land, which he leased to a tenant who was killed by Indians. Holland Coffee subsequently occupied the land, and Hart sued him and lost.
In 1840 Hart was killed in an altercation over this land by Silas C. Colville, a partner of Coffee. Colville claimed self-defense and was acquitted by a jury. After Hart's death his heirs sued again for the property and lost. Hart had brought his four children to Texas with him. His second wife, Prior, whose maiden name was Wallace, was either from North Carolina or from Georgia. They had six children. It is speculated that Wallace was a common-law wife and that her children were not legal heirs, since she lost a lawsuit that she filed in an attempt to claim part of Hart's assets.