State Highway 121 (SH 121) is a state highway angling from southwest to northeast through north central Texas. It runs from downtown Fort Worth, Texas at the junction of Interstate 35W to Bonham, Texas, just north of a junction with U.S. Highway 82. Between Fort Worth and Euless, SH 121 is known as Airport Freeway (east of Euless, this name applies to SH 183). East of Coppell, the highway functions as the frontage road for the Sam Rayburn Tollway, a toll road that runs northeast to McKinney. From McKinney to Melissa, the state highway is concurrent with US 75 and the North Central Expressway. Northeast of Melissa, SH 121 is a less-traveled roadway often referred to as the Sam Rayburn Highway. From Wikipedia
