Today is Women’s Equality Day and the 90th anniversary of the effective date of the 19th Amendment, which guaranteed equal political rights for women. It may seem unbelievable to many Americans today, but for most of this country’s history, women were denied the franchise in states across the country (some states allowed women to vote before ratification of the 19th Amendment, others did not).

Indeed, the story is even more complicated and disturbing than that: as part of the otherwise inspiring and momentous adoption of the 14th Amendment in 1868, which enshrined birthright citizenship and equal civil rights and due process for all Americans, the Constitution actually allowed the denial of political rights to women, imposing a sanction only on the denial of the vote to “male inhabitants” of a state. This was the first use of a gender specific term in the Constitution, and some women’s rights advocates opposed ratification of the 14th Amendment on this basis.

The adoption of the 19th Amendment in 1920 reflects the arc of our constitutional progress. Americans rightly celebrate the Constitution’s 1787 Framers for creating the best and most durable form of government in world history. But we should all also be keenly aware of the important blind-spots in the amazing vision of the white men gathered in Philadelphia in 1787. It took the heroic labors of successive generations of Americans to eliminate slavery, give women the vote, and create the increasingly “more perfect union” we live in today. In a brilliant speech supporting the confirmation of Justice Sonia Sotomayor, Senate Judiciary Committee Chairman Patrick Leahy called our constitutional history a “journey” that:

began with improvements upon the foundation of our Constitution through the Bill of Rights, and then continued with the Civil War amendments, the 19th Amendment’s expansion of the right to vote to women, the Civil Rights Act of 1964 and Voting Rights Act of 1965, and the 26th Amendment’s extension of the vote to young people. These actions have marked progress along the path of inclusion, and have recognized the great diversity that is the strength of our great Nation.

This story of constitutional redemption should inspire all Americans, but progressives particularly because progressive social movements have been the motivating force behind just about every successful effort to make our Constitution better. At the same time, progressives should be focused hard and energized in response to the constitutional agenda of the Tea Party, which seeks to return to the America of the 1787 Framers and, as Jim Linn, a Tea Party member from San Diego explained to the Washington Post, this “would mean scrapping a lot of the Amendments.”

Nevada Senate candidate Sharron Angle, and others, have called for repeal of the 16th Amendment, which reinstated the progressive income tax. Utah Senate candidate Mike Lee, and others, have called for repeal of the 17th Amendment, which provided for direct election of Senators. And established politicians on the right including Senator Lindsey Graham are now calling for repeal of the Citizenship Clause of the 14th Amendment — which guarantees that everyone born in this country is automatically a citizen — an effort that, if successful, would be the first time in history we have amended the Constitution to make it less egalitarian.

In short, today as we celebrate the 19th Amendment, the progressive story of our constitutional history — the story of our still unfinished constitutional journey towards a more perfect union — is under assault.

This weekend — the weekend 47 years ago when Martin Luther King inspired the nation and the world with his “I have a dream speech” — Glenn Beck and Sarah Palin will be rallying at the Lincoln Memorial, the site of Dr. King’s speech, for an event designed to “restore honor” and return us to our “nation’s founding principles.” It is ironic that Beck, Palin, and their Tea Party friends chose the Lincoln Memorial to stage their rally, given that they tend to ignore the constitutional progress urged by Lincoln, secured through a bloody civil war, and written into the Constitution in the post-war amendments — except, of course, when they are calling to repeal part of these amendments.

As the shouts of Beck and Palin dominate the news this weekend, progressives should ensure that the words etched on the Lincoln Memorial are not forgotten in the midst of Tea Party rhetoric. As Lincoln made clear in his Gettysburg Address, the United States was “conceived in liberty, and dedicated to the proposition that ‘all men are created equal,’” but it was only after the Civil War and several constitutional amendments that our country experienced “a new birth of freedom” and the promises of our Nation’s Founding were kept.

Progressives have a great answer to the calls from the Tea Party to a return to our founding principles: the Constitution we have today is better because of a series of Amendments that have made the nation more free, more equal and capable to meet the challenges of the 21st Century world. Today’s anniversary of the 19th Amendment — and the very sight of the Lincoln Memorial at Saturday’s rally — should be timely reminders of that constitutional progress. We need to get that story out.