State Highway 16 is a 14 mile (22 km) route connecting State Highway 44 and Star with Emmett.

Also known as the Emmett Highway, Highway 16 begins at the junction of State Highway 44 near Star and Eagle. The highway continues north through Jackass Gulch and descends over 500 vertical feet (152 m) on the Freezeout Grade into the Emmett Valley. The highway then curves westward for a short distance, where it terminates at the junction with State Highway 52 just south of the Emmett city limits .

This route has been in existence since 1929. Originally, the alignment terminated in Horseshoe Bend. In 1938, the northern section of the alignment from Emmett to Horseshoe Bend was then replaced by State Highway 52. When this happened, the highway then realigned to the west, terminating in New Plymouth. The route was truncated at its current terminus in Emmett in 1955 when Highway 52 was extended on to its northern section heading toward New Plymouth.

In 2007, plans are underway to extend State Highway 16 south of its current terminus to Interstate 84. A new interchange at the interstate is being studied as part of this plan, which will be built somewhere between Black Cat Road and Robinson Blvd. The new highway is planned to be a 4-lane divided limited-access expressway or freeway, and will require a new river crossing over the Boise River. This project is part of the ITD GARVEE Transportation Program.

As of December 2012, construction has begun on the Boise River Bridge section between SH-44 and US-20/26; it is expected to be substantially completed by September 2014.