US President Barack Obama said farewell in his last major speech of his presidency, against the background of the most toxic election campaign in recent US history and a host of new threats against American democracy.

"For all our outward differences, we all share the same proud title: Citizen," Mr. Obama told the crowd of 20,000 fans and well-wishers at Chicago's McCormick Place Convention Center. 

"Ultimately, that's what our democracy demands.  It needs you.  Not just when there's an election, not just when your own narrow interest is at stake, but over the full span of a lifetime," he said, urging people to step up their involvement in the political process.  "If you're tired of arguing with strangers on the internet, try to talk with one in real life.  If something needs fixing, lace up your shoes and do some organizing.  If you're disappointed by your elected officials, grab a clipboard, get some signatures, and run for office yourself.  Show up.  Dive in.  Persevere.  Sometimes you'll win.  Sometimes you'll lose."

The outgoing president insisted that Americans shouldn't give in to despair and cynicism, and especially not to the racism that fueled his successor's ugly path to the White House:  "If every economic issue is framed as a struggle between a hard-working white middle class and an undeserving minority, then workers of all shades will be left fighting for scraps while the wealthy withdraw further into their private enclaves," said Obama noting that America's enemies are emboldened if the nation is divided.