Since Trump has taken office, his first orders as president have sparked a wave of activism around the US.
On April 22, hundreds of thousands will come out for the Scientists' March on Washington, while many more are expected to protest at the People's Climate March a week later.
The efforts will follow local rallies in cities around the country, as well as two large NYC strikesfrom groups that could be affected by President Donald Trump's executive order that would temporarily bar immigrants and refugees from seven majority-Muslim countries.
But the biggest one-day protest after Trump's inauguration was the Women's March, which drew around a half million people in DC.
"In the spirit of democracy and honoring the champions of human rights, dignity, and justice who have come before us, we join in diversity to show our presence in numbers too great to ignore,"the Women March's site reads.
Here's a look back at some of the biggest marches in American history.
The March on Washington for Jobs and Freedom — August 28, 1963
Approximately 250,000 people participated in this 1963 civil rights march in DC, where Martin Luther King Jr. delivered his famous "I have a Dream" speech.
An anti-Vietnam War protest in Washington DC — November 15, 1969
Between 500,000 and 600,000 people demonstrated against the Vietnam War in DC, which had led to thousands of deaths by 1969. Coalitions started organizing smaller rallies in 1967, eventually leading up to the large anti-Vietnam march two years later.
The Solidarity Day march in Washington, DC — September 19, 1981
The Solidarity Day march was a rally of about 260,000 people in DC in 1981. It was in response to President Ronald Reagan's decision to fire 12,000 air traffic controllers who went on strike and demanded wage increases and safer working conditions.
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