The day after the mass shooting at Sandy Hook School in Newtown, Connecticut, I started a Facebook page calling on American mothers and women to rally around "gun sense" - the simple idea that we can do more to protect our families and children from gun violence.
The response was overwhelming. Within weeks, Moms Demand Action moved from an online idea to an offline movement with volunteers showing up on Capitol Hill and in statehouses and corporate boardrooms. Today, as part of Everytown for Gun Safety, we're a national grassroots movement with chapters in every state and more than three million supporters.
How did we grow so quickly and become so effective? The answer is simple: the power of women. Women are unparalleled multi-taskers with relentless energy and stubborn drive - especially when it comes to protecting our children and families. Harness that momentum into a women-led movement and it's unstoppable.
That's why I was so heartened when I saw on Facebook that a women's march in Washington, D.C., was forming just hours after Donald Trump was elected president. Like Moms Demand Action, the battle cry for a national demonstration was started online by a few women and was quickly answered by women en masse.
Now hundreds of thousands of women and supporters will come together this weekend at the Women's March on Washington - as well as hundreds of sister marches across the country - to oppose policies and rhetoric that denigrate and endanger women, and to demonstrate our strength in numbers and diversity.
This is nothing new: women have always been on the front lines of activism in America, from opposing child labor to fighting for civil rights to creating laws against drunk driving. Some of the women who fought these battles were disbelieved, harassed, attacked and even imprisoned, but they did not stand down. And neither will we.
I'll be marching alongside hundreds of Moms Demand Action volunteers because gun violence is a women's issue:
· American women are 16 times more likely to be killed with a gun than in other high-income countries;
· In an average month, 50 women are shot to death by a current or former partner in the United States;
· Approximately 4.5 million American women have been threatened with guns, and guns are the weapon of choice in domestic violence murders.
I'm also marching because the lobbying organization that donated more than $30 million to Donald Trump's campaign - the National Rifle Association - is a direct threat to women everywhere. Their leadership has a history of misogyny - from describing women as "b*tches" and "c*nts" to downplaying rape.
And the policies they lobby for make it easy for domestic abusers to get their hands on guns. As the largest outside donor to Trump's presidential campaign, the NRA has been emboldened to push their deadly agenda now more than ever.
Our volunteers and survivors won't fall in line - we'll hold the line. We've become the David to the NRA's Goliath, loosening the gun lobby's stranglehold by passing gun safety laws, defeating dangerous bills, and getting businesses to adopt policies that protect customers and employees.
And while America's gun violence crisis turned me into a single-issue voter, women do not and cannot lead single-issue lives. Using our voices and votes, we also have to push back against the misogyny, racism, homophobia, xenophobia, anti-Semitism, and anti-immigrant rhetoric that shaped the 2016 election.
Women are the majority in America, and there is strength in numbers. But showing up on Saturday is only half the battle. The other half is keeping the march momentum going back at home and in our communities until the next election, and the election after that.
The Women's March on Washington isn't about one day or one event: it's about the future of our nation. As Martin Luther King, Jr., said in 1963 at the March on Washington for Jobs and Freedom, "We cannot walk alone. And as we walk, we must make the pledge that we shall always march ahead. We cannot turn back."
After the Women's March on Washington, I pledge to keep walking with an army of Americans who want to live in a nation free of senseless gun violence, and who want equal rights, protections and equality for all Americans - regardless of their gender. Saturday is just the beginning, and there's no turning back.