WASHINGTON – Crowds descended on Chincoteague Island in Virginia on Wednesday for the 87th annual pony swim, made famous in Marguerite Henry’s 1947 book “Misty of Chincoteague.”

Every year, the wild ponies of Assateague Island are rounded up and herded off the island to swim to nearby Chincoteague, where some of them are later auctioned. The swim takes less than five minutes, but the annual tradition, known as Pony Penning Day, attracts tens of thousands of people each year.

On Thursday, the foals will be auctioned to raise money for the Chincoteague Volunteer Fire Department. In 2011, 69 ponies were sold for an average cost of $1,442. In total, the auction raised $99,500.

The auction also helps maintain the size of the Assateague herd, which is around 150.

On Friday, the ponies will swim back to their home island where they live year-round.

Here’s a look at the 2010 event:

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