Demonstrators were asked to wear face coverings and practise social distancing amid the coronavirus pandemic.
The group behind the Women's March, which is held in January, called on women across the country to organize events following the death of Supreme Court Justice Ruth Bader Ginsburg and the Republican Party's decision to push through a replacement before the November 3 presidential election.
A number of protesters dressed in red robes and white bonnets, portraying characters forced to bear children in the dystopian novel and television series "The Handmaid's Tale".
At the same time, the organization Voz das Mulheres Independentes promoted a concentration of support for Judge Amy Coney Barrett in front of the Supreme Court headquarters. Many protesters in Washington said they were angry because Trump's Republicans were ready to elect Barrett to the top U.S. justices ahead of the November 3rd presidential election. With it, the Conservative Supreme Court justices would be in the majority with six to three votes, possibly for decades.
Barrett has made no secret of her strong Catholic beliefs, raising concerns that a Supreme Court dominated by conservatives could overturn abortion rights if she is confirmed by the Senate.
The protesters marched through downtown Washington to the Supreme Court steps. "And this is the biggest thing that I know that I could do to help make change".
Rachel O'Leary Carmona, the Executive Director of the Women's March said, "We are sicker".
Dozens of other rallies were planned from NY to San Francisco to signal opposition to Mr Trump and his policies, especially the push to fill the seat of Justice Ginsburg before election day.
"His presidency began with women marching and now it's going to end with woman voting".
Several events took place in Manhattan Saturday, including one that started with a rally in Washington Square Park before participants marched to join another rally at the New York Stock Exchange.
"Vote for your daughter's future", read one message in the sea of signs carried by demonstrators.
More than 26 million Americans have already cast their ballots for who they want to sit in the White House for the next four years, Trump or his Democratic rival Joe Biden.