There are
984 mi
from Longmont, CO to Glendale Heights, IL
That's the driving distance. It would take 17 hours 38 mins to go from Longmont, Colorado to Glendale Heights, Illinois.
The flight distance (direct flight from Longmont, CO to Glendale Heights, IL) is 893.81 mi.
984 mi = 1,583.01 kms