There are
832 mi
from Longmont, CO to Seagoville, TX
That's the driving distance. It would take 15 hours 21 mins to go from Longmont, Colorado to Seagoville, Texas.
The flight distance (direct flight from Longmont, CO to Seagoville, TX) is 704.48 mi.
832 mi = 1,339.39 kms