President calls on all Americans to unite to protect the nation’s democracy.

In a farewell address to a hall filled with the activists who helped him become the first black American president, Barack Obama Tuesday urged all Americans to unite to protect the nation’s democracy, which he said is being threatened by outside forces as well as tensions within.

Beyond economic and national security threats, the president said two other forces threaten the nation’s future: race relations and a hardening political divide riven by disputed facts such as the veracity of global warming and human contributions to it.

While acknowledging progress for the black community, Mr. Obama said the nation needed to do more and to broaden the discussion to include other minorities whose children also will inherit the nation. “If we decline to invest in the children of immigrants, just because they don’t look like us, we diminish the prospects of our own children —because those brown kids will represent a larger share of America’s workforce,” he said.

Mr. Obama’s decision to deliver his speech in his hometown of Chicago, where he first addressed the country after his historic 2008 victory, is a departure from the traditional settings his predecessors have chosen for their farewell addresses. It is intended to mark a symbolic closure to the political movement that propelled him to the White House.

Mr. Obama’s decision to deliver his speech in his hometown of Chicago, where he first addressed the country after his historic 2008 victory, is a departure from the traditional settings his predecessors have chosen for their farewell addresses. It is intended to mark a symbolic closure to the political movement that propelled him to the White House.

His remarks also deviated from the norm in both scope and intensity. Mr. Obama, who campaigned aggressively against his successor, president-elect Donald Trump, often told his supporters that all the progress of the last eight years “goes out the window” if Americans elect “somebody who has proven himself unfit to lead or represent this country that we love.”

On Tuesday, he referred just once to Mr. Trump, who has vowed to dismantle much of Mr. Obama’s policies when he takes office on Jan. 20. “In 10 days, the world will witness a hallmark of our democracy: the peaceful transfer of power from one freely-elected president to the next,” Mr. Obama said, shushing those in the crowd who shouted in protest. “I committed to President-elect Trump that my administration would ensure the smoothest possible transition, just as President Bush did for me. Because it’s up to all of us to make sure our government can help us meet the many challenges we still face.” Just 13 of the 44 presidents have delivered farewell addresses, though every one since Harry S. Truman in 1953 has done so.

Mr. Obama addressed the country still popular among Americans. A Wall Street Journal/NBC News poll in December found he has a 52% approval rating, with 42% disapproval. Mr. Obama defended policies he sees as the benchmarks of his legacy. On the domestic front, that included the economy’s recovery from the biggest recession since the Great Depression at the turn of the last century and his health-care law. In terms of foreign policy, Mr. Obama pointed to the reduction of U.S. troops serving in Iraq and Afghanistan, although his promise to end both of those wars is unfulfilled and he has opened new military fronts against terrorist groups in other countries such as Syria, Libya and Yemen. Mr. Obama also highlighted his re-establishment of U.S. relations with Cuba, a deal with Iran to restrain its nuclear program and an international climate-change agreement.

Mr. Trump has criticized Mr. Obama on all of those policies

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