At the end of the movie, Hopkins uses the money he won to save a band of mustangs from slaughter. The horses are released from their pens and begin to gallop off.

Back to Hopkins: he removes Hidalgo's saddle and bridle and releases him. Hidalgo walks off to join the band of mustangs and is soon galloping alongside them. Note how prettily the sunlight glints off the metal shoes on Hidalgo's hooves.

OOPS! Major no-no! Faux pas extraordinaire! Even horses put to pasture for a few weeks have their shoes removed to prevent any damage that can occur with a loose or missing shoe. I think the Hidalgo's horse wranglers fell asleep near the end of the movie. He should have been released unshod :)