There are
1,036 mi
from Longmont, CO to Rantoul, IL
That's the driving distance. It would take 18 hours 16 mins to go from Longmont, Colorado to Rantoul, Illinois.
The flight distance (direct flight from Longmont, CO to Rantoul, IL) is 892.49 mi.
1,036 mi = 1.61 kms