Business Loop I-5 - Castle Rock

Business Route I-5

I-5 south at Business Loop I-5 to Castle Rock, Washington — Interstate 5 south at the off-ramp for Business Loop I-5 at Castle Rock, Washington. The Castle Rock business loop is the only remaining business route for I-5 in Washington. A handful of routes remain in service along I-90 as well. 09/02/06

The Castle Rock business route circles west from I-5 along Huntington Avenue (old U.S. 99) between Exits 48 and 49. The northern half of the 2.9 mile loop doubles as Washington State Route 411. The route is poorly marked through the Castle Rock city center.

Updated August 4, 2026