There are
2,687 mi
from San Marcos, CA to Hyattsville, MD
That's the driving distance. It would take 1 day 23 hours to go from San Marcos, California to Hyattsville, Maryland.
The flight distance (direct flight from San Marcos, CA to Hyattsville, MD) is 2,263.73 mi.
2,687 mi = 4,324.34 kms