There are
1,520 mi
from Thornton, CO to North Tonawanda, NY
That's the driving distance. It would take 1 day 3 hours to go from Thornton, Colorado to North Tonawanda, New York.
The flight distance (direct flight from Thornton, CO to North Tonawanda, NY) is 1,363.94 mi.
1,520 mi = 1.61 kms