I love pumpkin pie — but not just any pumpkin pie.

It has to be my mother’s pumpkin pie, made with her unique thick and dry crust, and it has to be enjoyed only on Thanksgiving Day.

It’s a Purcell family tradition, after all, and tradition is the reason Thanksgiving is my favorite American holiday.

The very first recorded Thanksgiving occurred in November 1621 when the Plymouth colonists enjoyed their first corn harvest and invited the Wampanoag to share a three-day feast to give thanks for their bounty and to express their gratitude to the tribe for helping them adapt to, and survive in, the new land.

According to History.com, there’s some controversy over the first Thanksgiving.

Similar events may have taken place earlier in other parts of North America and, given the bloody conflict among Native Americans and European settlers that took place over many years, there’s also disagreement about how peaceful and friendly the first thanksgiving really was.

For the next few centuries, as America flourished, individual colonies and states celebrated various kinds of thanksgiving events.

It didn’t become an official holiday until 1863, when, in the midst of the destructive Civil War, President Abraham Lincoln proclaimed a national Thanksgiving Day to be held each November.

It didn’t take much time after that for Thanksgiving to evolve into its current customs and formalities.

My great grandfather, who came to America from Ireland in the 1880s and his wife, whose parents came from Alsace Lorraine, likely celebrated it the same way my extended family still celebrates it.

They ate too much turkey, mashed potatoes and gravy, cranberry sauce and fresh-made muffins.

They found room for a piece of pie covered in whipped cream, then sat around the messy dinner table sipping coffee, talking and laughing and feeling thankful for their bounty.

Their tradition didn’t involve NFL football games, as ours now does, nor my mother’s version of pumpkin pie.

Truth be told, the staples that many of us enjoy each Turkey Day were not a part of the first Thanksgiving.

In 1641, when Governor Bradford wrote a book about the history of the Plymouth settlement, he described the bountiful spread at the first Thanksgiving.

He wrote that the settlers and the Wampanoag consumed geese, duck and venison — and likely lobster, seal and swans.

They had no potatoes, since they didn’t yet grow in North America.

There was no cranberry sauce, because the colonists didn’t begin boiling berries with sugar until 1671.

There wasn’t any bread because they had no ovens. And though pumpkins were plentiful, it’s doubtful they had the butter and wheat flour they needed to make pie crust.

So how did the country end up with a day devoted to gorging ourselves on turkey and all the fixings?

In the late 1840s through the 1860s Sarah Josepha Hale, an editor of a popular magazine, lobbied hard to have Thanksgiving proclaimed a national holiday. She succeeded.

She also published many recipes that featured the turkey and trimmings that are now the core of the traditional Thanksgiving meal.

But the specifics of how we arrived at our annual Thanksgiving feast are not so important.

What’s important is that the day always be a common celebration that unites Americans — a day in which we honor past generations and pass on our shared, ever-evolving rituals to the next.

Now if you’ll excuse me, I have a piece of pumpkin pie to devour!

Tom Purcell is an author and humor columnist for the Pittsburgh Tribune-Review. Email him at Tom@TomPurcell.com