Originally constructed as a two-lane highway, the northern segment of the route, from US 90 in western San Antonio to Kitty Hawk Road in northeastern Bexar County, has been upgraded to a four-lane freeway.

The highway continues to the west to an interchange with SH 16, passing to the south of the Toyota Motor Manufacturing Texas plant.

The loop continues north near the campus of Northwest Vista College to a junction with the western terminus of SH 151.

The intersection is signalized but southbound traffic is not required to stop due to no left hand turns from SH 151 to Loop 1604.

The freeway begins to head east at the Babcock Road interchange and passes near the UTSA main campus, the Shops at La Cantera and Six Flags Fiesta Texas.

Upon leaving San Antonio, the freeway enters the Live Oak city limits before a cloverleaf interchange at I-35.

The same applies to two former at-grade turn-offs southeast of the Kitty Hawk Road interchange at Meadowland Drive and Byrd Boulevard.

The highway passes by the western boundary of Randolph Air Force Base before curving to the south.

The highway re-enters San Antonio city limits prior to its interchange at I-10 at its official beginning and end.

TxDOT has expanded the project further south to SH 151 and US 90, creating a direct flyover overpass from southbound Loop 1604 to eastbound US 90.

[13] TxDOT plans to widen Loop 1604 from four lanes to ten between SH 16 (Bandera Road) near Helotes and I-35 in Universal City.