There are
2,448 mi
from San Marcos, CA to Monroeville, PA
That's the driving distance. It would take 1 day 19 hours to go from San Marcos, California to Monroeville, Pennsylvania.
The flight distance (direct flight from San Marcos, CA to Monroeville, PA) is 2,111.90 mi.
2,448 mi = 3,938.89 kms