SONIC Drive-In Address: 417 Highway 37 S., Mount Vernon, TX 75457 Phone: (903) 537-4596 Restaurants, Foods-Carry Out, Sonic Drive In Other Businesses: Lucky 7 Pit Stop at 1319 Holbrook St, Mount Vernon, TX 75457 Milano's Pizza at 114 Kaufman St S, Mount Vernon, TX 75457 Sonic at 417 Texas Highway 37, Mount Vernon, TX 75457