(KDKA) – Today is a uniquely American national holiday, but Thanksgiving wasn’t always celebrated nationwide.

How did this holiday become such an American tradition?

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CBS Pittsburgh’s Jon Delano says Thanksgiving has always been special for his family. His ninth great-grandfather, Philippe de Lannoy, arrived in Plymouth in late 1621 after the first Thanksgiving and has often wondered what he missed when 90 Native Americans and 52 Pilgrim survivors enjoyed the first harvest feast.

“There are two eyewitness accounts of that event which was a three-day harvest festival with lots of feasting and fellowship. But it wasn’t until two years later that the Pilgrims used the word Thanksgiving,” says Melanie Kirkpatrick, author of “Thanksgiving: The Holiday at the Heart of the American Experience.”

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Kirkpatrick, who has written about the history of Thanksgiving, says the Pilgrims owed a great deal of thanks to the native Wampanoag Indians who taught them how to survive in those early years.

“It does point the way, in my view, to the multi-cultural diverse people we’ve become 400 years later,” she says.

In fact, the first menu had food from both Pilgrims and Indians — turkey, venison, squash and corn but no mashed potatoes, cranberry sauce or pumpkin pie!

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Read the rest of the story on CBSPittsburgh.com.