There are
836 mi
from Gaithersburg, MD to Cape Girardeau, MO
That's the driving distance. It would take 15 hours 41 mins to go from Gaithersburg, Maryland to Cape Girardeau, Missouri.
The flight distance (direct flight from Gaithersburg, MD to Cape Girardeau, MO) is 679.93 mi.
836 mi = 1,344.72 kms