There are
1,521 mi
from Great Falls, MT to Grapevine, TX
That's the driving distance. It would take 1 day 3 hours to go from Great Falls, Montana to Grapevine, Texas.
The flight distance (direct flight from Great Falls, MT to Grapevine, TX) is 1,251.07 mi.
1,521 mi = 2,448.59 kms