State Highway 91 or SH 91 is a state highway in the U.S. state of Texas that runs 13.6 miles (21.9 km) from Sherman through Denison to the Oklahoma border at Denison Dam at Lake Texoma (where it connects with Oklahoma State Highway 91) . This route was designated in 1994, the northern segment replacing State Highway 75A (designated in 1946 as an alternate route to US 75 after Denison Dam was completed the previous year) and the southern segment designating the old route of U.S. Highway 75 which was rerouted and upgraded to freeway status. The highway is known locally as Texoma Parkway for much of its length, except through some parts of Denison. It is one of the main commercial strips in the Sherman-Denison Metropolitan.