There are
971 mi
from Gaithersburg, MD to Marshalltown, IA
That's the driving distance. It would take 18 hours 2 mins to go from Gaithersburg, Maryland to Marshalltown, Iowa.
The flight distance (direct flight from Gaithersburg, MD to Marshalltown, IA) is 846.79 mi.
971 mi = 1,561.93 kms