There are
807 mi
from Gaithersburg, MD to Macomb, IL
That's the driving distance. It would take 16 hours 3 mins to go from Gaithersburg, Maryland to Macomb, Illinois.
The flight distance (direct flight from Gaithersburg, MD to Macomb, IL) is 720.08 mi.
807 mi = 1,298.79 kms