There are
1,652 mi
from San Marcos, CA to Maryville, MO
That's the driving distance. It would take 1 day 5 hours to go from San Marcos, California to Maryville, Missouri.
The flight distance (direct flight from San Marcos, CA to Maryville, MO) is 1,326.20 mi.
1,652 mi = 1.61 kms