A UFC Freedom 250 event on the South Lawn of the White House — with a 5,000-seat temporary stadium and 85,000 tickets for viewing on massive screens on the Ellipse — has sparked controversy. The event is unprecedented, and it falls on President Trump’s birthday.

Put aside what you think of Sunday’s extravaganza. There is still a good reason to embrace June 14: Flag Day.

Those allergic to all things Trump should remember that Flag Day existed decades before he was born and, God willing, will endure for generations after.

Flag Day has a long tradition. Yet if not for its coincidence with Trump’s birthday, it would likely pass with little notice. That is a mistake. This is not a call to worship a colorful banner. It is a call to remember that Americans — left, center, and right — are united by founding principles from the Declaration of Independence, represented by Old Glory.

On June 14, 1777, the Second Continental Congress approved a resolution establishing a uniform national flag. The 13-star flag, commonly associated with Betsy Ross, became a rallying banner and a source of pride. It was not yet revered as it would be later, but it symbolized the freest nation in world history.

Then came the Civil War and the lowering of the flag over Fort Sumter. That image triggered an outpouring of love for Old Glory.

Jonathan Flynt Morris, a banker and strong Republican Unionist, urged Charles Dudley Warner, editor of the Hartford Evening Press, to write about the need not merely to respect the flag, but to revere it. On June 10, 1861, Warner followed that advice and proposed a new holiday: Flag Day.

“This flag is our dearest symbol of nationality,” Warner wrote. “It stands for civil liberty on this continent. To keep it full high advanced is our highest pride; to strike at it is to arouse all the passion of the nation to defend it, and to punish the perpetrators of the outrage.”

Flag Day celebrations began in Warner’s home state of Connecticut. They slowly spread to schools in Wisconsin in 1885, New York schools in 1889, and then to Philadelphia and public buildings in New York state in 1894. An American Flag Day organization was created to further the movement.

President Woodrow Wilson, a Democrat, issued the first federal recognition of the holiday on May 30, 1916. Wilson’s proclamation called for patriotic exercises that would “give significant expression to our thoughtful love of America” and our understanding of “the great mission of liberty and justice to which we have devoted ourselves as a people.”

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He also called Americans to rededicate themselves to the principles of “independence, liberty, and right,” which no person “can corrupt” and no influence could draw away from their ideals. Finally, on Aug. 3, 1949, President Harry S. Truman, also a Democrat, signed an act of Congress designating June 14 of each year as National Flag Day.

Flag Day exemplifies our shared American creed. It was the brainchild of Republicans, spread outside party politics, and was instituted nationally by Democrats. Its purpose is to recommit us to the founding principles declared in the Declaration of Independence and embedded in the Constitution: equality, limited government, the rule of law, unalienable rights, the social compact, and the right to alter or abolish oppressive government.

America did not fully live by those principles in 1776, and we do not perfectly live by them today. But belief in those principles has inspired generations of patriots to move us closer to their fulfillment. Abolitionism, women’s suffrage, and the civil rights movement all called upon America’s first principles to push the country toward its promise. At its best, our flag stands for liberty and equality.

Those allergic to all things Trump should remember that Flag Day existed decades before he was born and, God willing, will endure for generations after. It is not about one man. It is a call for all Americans to unite around the principles that made the country possible.

We should answer that call.