There are
815 mi
from Longmont, CO to Midlothian, TX
That's the driving distance. It would take 15 hours 4 mins to go from Longmont, Colorado to Midlothian, Texas.
The flight distance (direct flight from Longmont, CO to Midlothian, TX) is 696.20 mi.
815 mi = 1,311.05 kms