On the day after President Obama’s historic announcement of a plan to protect millions of illegal immigrants from deportation, hundreds of Latino activists and families gathered in front of the White House on Friday afternoon to express their gratitude — and also vow to press Congress to finish the job.

“The decision of the president is going to change the lives of 5 million people forever,” said Gustavo Torres, executive director of CASA de Maryland and Virginia, the major regional advocacy group for illegal immigrants, shortly before the rally. “Today is a day for all of us to celebrate and thank him for delivering on his promise. We are all very touched and moved by what he has done.”

At the same time, Torres said Friday will be the “last day of celebration,” because the immigrant community needs to turn its attentions immediately to Congress and the unfinished business of comprehensive immigration reform.

“We need to get ready to continue the fight,” said Torres, whose organization is one of five groups that sponsored the rally in Lafayette Square. “We have made history, but we cannot wait, because millions of people have still not gotten the help they need. We need to start pushing the Republican Party really hard to pass a bill.”

Some immigrants at the rally, which was attended by about 200 to 300 people, expressed mixed emotions about Obama’s announcement. They said they were grateful for his efforts but disappointed that the president had stopped short of legalizing several million other people, including many adults with no children and others whose children gained legal status under his 2012 order.

View Graphic From 2009 to 2012, the number of undocumented immigrants has dropped in 14 states and increased in seven states.

Kevin Escobar, a 17-year-old who crossed the border eight months ago to be reunited with his mother in the District, said young people like him would also like to get some relief.

“I am happy for the people who will benefit from this and will get their papers, but there are many others who are here in search of safety and a better future,” said Escobar, who said he left his native El Salvador to escape gang violence.

“You are at risk of dying just because you are young,” he said. “I had no other choice, but to come here.”

His mother, who has been in the United States for 11 years, won’t qualify under Obama’s plan, he said. “She has worked hard and has paid her taxes, but she is not covered because I wasn’t born here.”

Alejandra Sanchez, 42, a woman from Arizona with two legalized children, fasted outside the White House for more than a week to call attention to the plight of “dreamer moms” like her. On Friday, she said she felt admiration for Obama but also “a little disillusioned.”

She held up a poster that was printed with a message thanking the president, but she had written on it in Spanish, “Why did you leave out 6 million?”

A few feet away from the rally, a protester in military fatigues shouted through a bullhorn, “You are all illegal” and “Obama is the number one coyote,” using a word for guides who smuggle migrants into the United States. The man refused to identify himself to a reporter.

Here are the highlights from President Obama's speech on immigration, in which he outlined his executive action to shield 4 million illegal immigrants from deportation. (Ashleigh Joplin/The Washington Post)

Obama was not in the White House on Friday. He was in Las Vegas to attend a rally supporting his initiative.

The president’s action is expected to benefit about 4 million of the nation’s estimated 11 million illegal immigrants. CASA officials have predicted that could include up to 100,000 people in the Washington region, mostly from El Salvador, Honduras and Guatemala, who are parents of U.S.-born children or arrived in the country as children.

In order to obtain the three-year reprieve from deportation, they will need to provide immigrations officials with proof of a clean police record and their years of residency in the United States, as well as pay several hundred dollars in fees. Immigration offices are expected to begin receiving applications in six months.

Francisco Diaz, 40, an activist from Florida who spent much of the past several weeks with protesters in Lafayette Square, came to the rally early and said he planned to return to Miami on Saturday to start preparing immigrants there to apply for deferred deportation under Obama’s plan.

“We don’t want anyone to miss out on this chance,” he said. “People will need to start gathering documents, and we also want to tell them to watch out for lawyers and notaries who will try to cheat them.”