It then continued down present-day U.S. Highway 277 into San Angelo and Sonora and Del Rio.

On February 7, 1919, SH 4 was rerouted to end at Uvalde, and the old route from Sonora to Del Rio was cancelled.

This first one-mile (1.6 km) section was previously the final stretch of US 77 and 83 before they were rerouted to the southeast around downtown to the Veteran's International Bridge.

About a mile to the east is the cutoff for Farm to Market Road 2519, which leads to the Brownsville/South Padre Island International Airport.

SH 4 continues east, passing along the north side of the airport grounds and meeting intersections with Farm to Market Roads 313 and 511.

The highway continues east-northeast, past Boca Chica Village and SpaceX South Texas Launch Site, until it terminates at Boca Chica Beach and Brazos Island State Park on the Gulf of Mexico.