SH 85 was originally designated on August 21, 1923 along a route from Eagle Pass to Dilley via Carrizo Springs.

[3] On September 28, 1950, the section from Del Rio to Carrizo Springs was transferred to newly extended U.S. Highway 277.

The highway heads east from this junction and has an intersection with FM 1917 before leaving Carrizo Springs.

Heading east from Dilley, the highway turns back towards the northeast before crossing the Frio River.

SH 85 continues northeast to an intersection with FM 1582 before crossing into Atascosa County.