"As a direct result of the Trump administration's policy choices, there is a human rights disaster of epic proportions happening at our border", said Lorella Praeli, director of immigration policy and campaigns at the American Civil Liberties Union - another major organizer of the protests - in a statement last week announcing the demonstrations.
The president has faced renewed backlash in recent weeks over his administration's "zero tolerance" policy at the USA border, which has resulted in the separation of families.
630 women sat on the floor of the building's atrium in protest of the Trump administration's "zero-tolerance" policy that has separated families and has caused mass incarceration at the southern border.
As well as reuniting parents with their children, organisers are calling for an end to immigrant detention - even when families are kept together - and also plan to voice opposition to President Trump's travel ban targeting five majority-Muslim nations, which was upheld by the US Supreme Court earlier this week.
Under Mr Trump's "zero tolerance" policy, the government has begun prosecuting all migrants caught entering the country without authorisation. More than 600 marches are planned for 30 June, from immigrant-friendly cities like Los Angeles and New York City to conservative Appalachia and Wyoming under the banner Families Belong Together. "Our fight won't end until all mothers are reunited with their children, which is why we are demanding an end to immigrant detention once and for all".
Nevertheless, chanting "We Care" and "Abolish ICE", the protesters demanded Congress act to end Trump's policies regarding unlawful border crossings.
As a result of Trump's crackdown, distraught children were separated from their families and, according to widely broadcast pictures, held in chain-link enclosures, a practice that sparked domestic and global outrage.
There have been protests elsewhere in the country but Saturday's demonstrations are expected to be far larger, with 50,000 or more expected in Washington.
Among their targets: President Donald Trump, Attorney General Jeff Sessions and the agencies Immigration and Customs Enforcement and Customs and Border Protection.
The women, many of whom live outside the Washington area, said they planned to join in both protests while in town.
Since then, the United States government has reunited 538 children with their relatives, but more than 2,000 minors still remain separated, according to data from the Department of Homeland Security.
One of the first voices to call for the abolition of ICE was New York Democratic gubernatorial candidate Cynthia Nixon. "It's been motivating for us as advocates because we have to keep going". "I just reached a point where I felt I had to do more". "I don't think it's just part of the "resistance" energy we've seen since the election", Morales Rocketto said.