There are
948 mi
from Longmont, CO to Sycamore, IL
That's the driving distance. It would take 16 hours 53 mins to go from Longmont, Colorado to Sycamore, Illinois.
The flight distance (direct flight from Longmont, CO to Sycamore, IL) is 862.81 mi.
948 mi = 1,526.44 kms