It is a 19.7-mile (31.7 km) highway circling the city of Tyler in Smith County.

On October 30, 1957, with its southern portion now under construction, FM 1803 was redesignated as Loop 323.

The southern portion was to be designated as Loop 323 upon completion, while the northern portion — the original segments of the old FM 845 and FM 1803 — were resigned to coincide with the release of the 1958 official state highway map.

From there, Loop 323 travels south, intersecting its own "southern" terminus after 0.6 miles (0.97 km).

Shifting to a westward direction, it crosses US 69 and FM 2493 south of town, and SH 155 southwest of Tyler.