Gregg County was marked off from southern Upshur County by the Thirteenth Texas Legislature on April 12, 1873. The bill originally called the new county Roanoke, but during passage of the legislation the name was changed to Gregg, in honor of Confederate war hero John B. Gregg. Longview was selected as the county seat. By an act of the Fourteenth Legislature, on April 30, 1874, Gregg County was extended southward to add a portion of northern Rusk County.