Carrying signs that said "Justice and Dignity for All US Immigrants" and "We just want to work," the immigration activists filled five blocks of the National Mall.
Some protesters wore T-shirts that read, "Our journey as immigrants is a journey for human rights." New York Democratic Representative Nydia Velazquez said: "Every day without reform is a day that 12 million hard-working immigrants must live in the shadow of fear, and ... a day that a family is torn apart. That is wrong and it is unAmerican." Velazquez, who chairs the Congressional Hispanic Caucus, called on Congress and the president to reform immigration laws immediately.
Immigration is a sensitive issue in the United States where some 10.8 million illegal immigrants live and work in the shadows and where Hispanics, the largest immigrant group, are a rapidly increasing voting bloc.
Despite Washington's focus on health care, some in the ethnically diverse crowd were confident that lawmakers would hear about the rally and take note of their concerns.
"I have my documents, but the majority of the people here do not. It's time for all immigrants to support a just immigration reform. This country really needs it because... Latino labor produces a lot of money for their country," said a Colombian man who lives in Arlington, Virginia and gave his name as Jairo.
President Barack Obama benefited in 2008 from a huge Hispanic turnout, drawn by his promise to deliver immigration reform allowing millions of illegal immigrants a path to citizenship.
Frustrated that Obama has yet to fulfill a pledge to overhaul the nation's immigration system, immigration supporters have warned him to deliver this year or face the consequences in congressional elections in November.
"A lot of these people are here like myself are voters and if they don't do something, then I am voting against that congressman," said Gumecindo Salas, vice president of government relations for the Hispanic Association of Colleges and Universities.
While Hispanics are seen as unlikely to switch support to Republicans, who have fought immigration reform without a clampdown on illegal immigrants, they could hurt Democrats by failing to turn out at the polls.
On Thursday, Obama embraced a framework for legislation offered by Republican Senator Lindsey Graham and Democratic Senator Charles Schumer. Obama said the plan, which features a new high-tech identification card for US citizens and legal immigrants who want a job, "can and should be the basis for moving us forward."
But on Friday, Graham said, "If the healthcare bill goes through this weekend, that will, in my view, pretty much kill any chance of immigration reform passing the Senate this year." He and other Republicans have complained about the tactics used by Democrats to win support for the healthcare bill.
