There are
1,741 mi
from Harlingen, TX to Rockville, MD
That's the driving distance. It would take 1 day 8 hours to go from Harlingen, Texas to Rockville, Maryland.
The flight distance (direct flight from Harlingen, TX to Rockville, MD) is 1,484.69 mi.
1,741 mi = 2,802.54 kms