Route 50 is a 33-mile (53 km) road that stretches from Route 56 at the junction of Rice Street in Lihue to a point approximately 1/5 mile north of the northernmost entrance of the Pacific Missile Range Facility on the western shore of Kauai.

It is the longest numbered road on the island of Kauaʻi and is named Kaumualiʻi Highway.

The road passes through the only major shopping center on the island at the intersection with Route 58.

The National Historic Landmark known as Russian Fort Elizabeth is located where the highway crosses the Waimea River.

The only public services available west of Waimea are a collection of tourist shops and a convenience store at the base of Route 550.