There are
1,019 mi
from Thornton, CO to Montebello, CA
That's the driving distance. It would take 17 hours 50 mins to go from Thornton, Colorado to Montebello, California.
The flight distance (direct flight from Thornton, CO to Montebello, CA) is 829.50 mi.
1,019 mi = 1.61 kms