President Biden marked the 20th anniversary of the Department of Homeland Security on Wednesday by praising its 260,000 employees for allowing Americans to “live their lives” and “dream their dreams” after it was formed in the aftermath of the 9/11 attacks.

He said the work of the expanding agency is as important as ever, rattling off a growing list of responsibilities.

“Prevent terrorist attacks, domestically and globally, protect our air, land and sea borders,” Biden said at the DHS headquarters inside the St. Elizabeths campus in Washington. “Responding in an instant to natural disasters.”

“With the climate crisis, we are asking more of you every day, as extreme weather impacts communities with increasing frequency and ferocity,” the president said.

The department was formed by the Homeland Security Act of 2002 and began operations in 2003. Its portfolio is broad and includes immigration and border security services, elections and cybersecurity, the US Coast Guard, and the Federal Agency for Emergency Management, among other components.

“We’re going to continue to make sure that he has the resources to do his job because his job is very expansive across the board,” Biden said.

The president praised the agency for staying agile and adapting to new technological challenges in a rapidly changing world.

“I know the stakes and the stress of the job take an incredible toll, but each one of you answers the call every day,” he said. “You represent the best of us.”

Homeland Secretary Alejandro Mayorkas opened the festivities by noting that Mr. Biden voted for the creation of the agency as a Delaware senator.

“Twenty years, wow,” Biden said. “When we voted to establish them, no one thought it would be 260,000 people. But you’ve done an amazing job.”