Happy Thanksgiving Colorado! How well do you know this holiday's history?

Jolie Lee , Special for USA TODAY Network

Every year families gather around tables across the USA to celebrate Thanksgiving. But how did it become an official holiday?

The idea of creating a formal national holiday originated with Abraham Lincoln.

In an 1863 proclamation — amid the still-raging Civil War — Lincoln designated Thanksgiving to be celebrated on the fourth Thursday of November.

"He's the father of the whole idea of a nation giving thanks for its advantages and privileges of living in a democracy like this," Harold Holzer, historian and chairman of the Abraham Lincoln Bicentennial Foundation told USA TODAY.

The proclamation served another purpose for Lincoln. "He was always looking for ways to unify the nation in a terrible time of war," biographer Ronald C. White Jr. told USA TODAY.

Decades later, Franklin D. Roosevelt moved the holiday up a week, to the third Thursday of November, in part to lengthen the amount of time for holiday shopping.

Some states still insisted on celebrating Thanksgiving on the last Thursday, so eventually Congress stepped in.

On Dec. 26, 1941, less than a month after the attack at Pearl Harbor, Congress passed a law declaring the fourth Thursday of November as Thanksgiving Day.

Here are some other facts you might not know:

Informally, the U.S. government had recognized periodic days of thanksgiving from the start of the country's inception.

In 1777, a year after the Declaration of Independence, the Continental Congress declared a day of thanksgiving to celebrate a Revolutionary War victory over the British.

Click here to read more.