State Highway 48 (SH 48) runs from Brownsville to Port Isabel in Deep South Texas.

The route then travels across the sandy flats near the coast of the Gulf of Mexico, before reaching its eastern terminus at SH 100 on the far northwestern edge of Port Isabel.

[4] SH 48 was instead designated on that same day from Pharr through Harlingen to Brownsville, along the current route of U.S. Highway 83.

[5] On January 19, 1935, this route was swapped with SH 4, which ran closer to the Rio Grande along Military Highway, and was extended east out of the city to the Port of Brownsville.

[7] On October 28, 1973, SH 48, was signed to Port Isabel along Farm to Market Road 1792.