There are
1,725 mi
from Downey, CA to Watertown, SD
That's the driving distance. It would take 1 day 6 hours to go from Downey, California to Watertown, South Dakota.
The flight distance (direct flight from Downey, CA to Watertown, SD) is 1,347.05 mi.
1,725 mi = 1.61 kms