North Dakota Highway 21 (ND 21) is an east-west highway in North Dakota. The eastern terminus is at ND 6 about 5 miles (8.0 km) north of Breien and the western terminus is at U.S. Route 85 (US 85) about 5 miles (8.0 km) east-northeast of Amidon. The highway is known for the large number of abandonments located along it.

ND 21 runs east from its western terminus at US 85 for 15.7 miles before turning south onto ND 22 near New England for 8.1 miles. after the concurrency, ND 21 heads east for 28.7 miles, intersecting the Enchanted Highway and passing south of Regent, and sharing the road with ND 8 near Mott. In Mott, ND 21 turns off again to head east for the last 69.5 miles; along the way, ND 21 skirts north of Burt, picks up ND 49 near New Leipzig and exits the concurrency at Elgin, passes north of Heil and south of Carson, and meets the northern end of ND 31 near Flasher.

The current ND-24 segment between ND-6 and the current ND-24/ND-1806 junction was originally part of ND-21. This segment was renumbered between 1950 and 1963.

County	Location	mi	km	Destinations	Notes
Slope	​	0.0	0.0	US 85 – Belfield, Amidon, Bowman	Western terminus of ND 21
	​			ND 67 south – Scranton	Northern terminus of ND 67
Hettinger	New England			ND 22 north – Dickinson	Northern end of ND 22 concurrency
	​			ND 22 south – Reeder	Southern end of ND 22 concurrency
	​			ND 8 south – Hettinger	Western end of ND 8 concurrency
	Mott			ND 8 north – Richardton	Eastern end of ND 8 concurrency
Grant	New Leipzig			ND 49 south – Thunder Hawk	Western end of ND 49 concurrency
	Elgin			ND 49 north – Lake Tschida, Glen Ullin	Eastern end of ND 49 concurrency
Grant–Morton county line	​			ND 31 south – Raleigh	Northern terminus of ND 31
Morton	​			ND 6 – Mandan, Selfridge, Fort Yates	Eastern terminus of ND 21
1.000 mi = 1.609 km; 1.000 km = 0.621 mi       Concurrency terminus

• The North Dakota Highways Page by Chris Geelhart
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