It runs from Uvalde northwestward through the western Hill Country onto the Edwards Plateau, ending south of Sonora.

On October 10, 1927, it was extended south through Catarina and then east to Artesia Wells.

[6] On November 30, 1932, SH 55 was extended south through Batesville and Dilley to San Diego.

[10] The portion from Uvalde to 4.8 miles southeast of Batesville and from Divot to Dilley were to be constructed starting on March 26, 1942, but upon completion, these sections of SH 55 were to be cancelled and changed to Farm to Market Roads.

The section from Dilley to Divot was still under construction, but changed to FM 471 on July 9, 1945.