The southern segment of 7.97 miles (12.83 km) runs from Old Davidsonville State Park to Pocahontas.

[1] A northern segment of 14.57 miles (23.45 km) runs north from US 62/US 67 to the Missouri state line.

[2] AR 166 begins at Davidsonville Historic State Park in southwest Randolph County.

[1] AR 166 begins at US 62/US 67 (Future I-57) in east Pocahontas.

Media related to Arkansas Highway 166 at Wikimedia Commons