There are
2,705 mi
from San Marcos, CA to Havre De Grace, MD
That's the driving distance. It would take 2 days to go from San Marcos, California to Havre De Grace, Maryland.
The flight distance (direct flight from San Marcos, CA to Havre De Grace, MD) is 2,307.77 mi.
2,705 mi = 3.22 kms