There are
989 mi
from Hereford, TX to Mandan, ND
That's the driving distance. It would take 18 hours 56 mins to go from Hereford, Texas to Mandan, North Dakota.
The flight distance (direct flight from Hereford, TX to Mandan, ND) is 833.61 mi.
989 mi = 1,591.85 kms