There are
1,056 mi
from Amarillo, TX to Monrovia, CA
That's the driving distance. It would take 18 hours 9 mins to go from Amarillo, Texas to Monrovia, California.
The flight distance (direct flight from Amarillo, TX to Monrovia, CA) is 920.77 mi.
1,056 mi = 1,698.67 kms