SH 121, or State Highway 121, is a major highway located in the state of Texas. It runs approximately 30 miles, connecting the cities of Lewisville and McKinney. The highway serves as a vital route for commuters and travelers, facilitating access to various neighborhoods, businesses, and recreational areas. Originally constructed to ease traffic congestion in the rapidly growing Dallas-Fort Worth metropolitan area, SH 121 has undergone several expansions and improvements. It features multiple lanes, interchanges, and access roads, enhancing connectivity and supporting economic development in the region.