On January 21, 2017, the day after Donald Trump's presidential inauguration, over 4 million people in the United States marched in what became likely the largest single-day protest in American history. At the 2017 Women's March, women, men and children gathered to stand for equality, justice and tolerance — and this year, it's happening all over again. Here's what you need to know about the 2018 Women's March.

When is it happening?

Events are taking place across the world the weekend of January 20th. Many are taking place Jan. 20 while the #PowerToThePolls event is taking place Jan. 21.

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What is the #PowerToThePolls event?

This year, the co-presidents of the inaugural Women's March have organized an event in Las Vegas, Nevada, to celebrate the one-year anniversary of the march and launch #PowerToThePolls.

According to the Women's March website, #PowerToThePolls is a year-long "voter registration and mobilization tour" aimed at swing states across America. The tour will work to secure progressive seats in 2018 by registering voters and increasing support for women and progressive candidates. The first event is being held in Nevada because it's a swing state with the potential to turn blue in the midterm elections, and it's been the hub of some of the nation's most pressing issues, including gun violence and sexual harassment.

On the Women's March website, Tamika D. Mallory, co-president of the Women’s March said, “Women’s March has created a powerful movement that has ignited thousands of activists and new leaders. In 2018, we must turn our work into action ahead of the midterms. This new initiative will address voter registration and voter suppression head on. We marched for justice in DC, we created our plan in Detroit and now we’re bringing the power of the polls to Nevada.”

You can register for the event, here, and find the Facebook event, here.

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A few of the national co-chairs of the Women’s March at the 2017 Women’s March on Washington.

Are there marches, too?

Yes! There will be a Women’s March on NYC on Jan. 20, according to the Women’s March Alliance’s Facebook event. In New York City, a rally will begin at 11:30 AM and the march will begin around 12:30 PM. Currently, 19,000 people have said they are going on Facebook. You can register for the march, here.

There are also a number of sister marches taking place on Jan. 20, from Nashville, Tennessee, to Munich, Germany. Find some of those marches, here and here.