There are
1,621 mi
from Great Falls, MT to Seymour, IN
That's the driving distance. It would take 1 day 5 hours to go from Great Falls, Montana to Seymour, Indiana.
The flight distance (direct flight from Great Falls, MT to Seymour, IN) is 1,400.34 mi.
1,621 mi = 2,609.29 kms