Back in 1941, President Roosevelt made it official:

Thanksgiving became an annual custom throughout New England in the 17th century, and in 1777 the Continental Congress declared the first national American Thanksgiving following the Patriot victory at Saratoga. In 1789, President George Washington became the first president to proclaim a Thanksgiving holiday, when, at the request of Congress, he proclaimed November 26, a Tuesday, as a day of national thanksgiving for the U.S. Constitution. However, it was not until 1863, when President Abraham Lincoln declared Thanksgiving to fall on the last Thursday of November, that the modern holiday was celebrated nationally. 

With a few deviations, Lincoln's precedent was followed annually by every subsequent president--until 1939. In 1939, Franklin D. Roosevelt departed from tradition by declaring November 23, the next to last Thursday that year, as Thanksgiving Day. Considerable controversy surrounded this deviation, and some Americans refused to honor Roosevelt's declaration. For the next two years, Roosevelt repeated the unpopular proclamation, but on November 26, 1941, he admitted his mistake and signed a bill into law officially making the fourth Thursday in November the national holiday of Thanksgiving Day.

In my case, I did not know a thing about Thanksgiving when our family settled in Wisconsin in the fall of 1964.  I began to detect that something was coming when the kids in school started putting "turkey posters" about the upcoming holiday.  Finally, Miss Jones, that wonderful 6^th-grade teacher I was blessed with, sat me down and explained the story, from the ship crossing the ocean, to the landing at Plymouth Rock, to the terrible first winter and eventually a day to say thanks for everything.

It did not take long for me to get into the Thanksgiving mood.  

Today, it's my favorite American holiday for two reasons:

1) It demonstrates the role of faith in the early days of what would become the United States.

2) It confirms that this land was settled by self-reliant people who faced adversity and grew stronger.

As I told a friend years ago, you cannot understand American exceptionalism unless you get familiar with the Thanksgiving story. 

P.S. You can hear CANTO TALK here & follow me on Twitter @ scantojr.