The coastal island of Assateague is partly in the state of Virginia and partly in Maryland. The island is home to a herd of feral ponies, with a fence dividing the ponies into each state. On the Maryland side, they belong to the National Park Service. On the Virginia side, they belong to the Chincoteague Volunteer Fire Company, which thins the herd in July every year with a fundraising auction. But first they have to get the ponies off the island.
Every year the department's "saltwater cowboys" round up the island's feral equines for a low-tide swim from Assateague to Chincoteague, where the ponies are herded down Main Street and corralled for a later auction. The first foal to make it to shore is crowned King or Queen Neptune and made the prize of the festival's raffle drawing. The remaining ponies are later auctioned, either for personal ownership or as "buybacks," in which case the pony will be returned to its island home for another year of feral roaming.
But how did the ponies get on the island in the first place? No one knows for sure, but you can read about the legend behind them at Atlas Obscura. Link
(Image credit: Bonnie U. Gruenberg)