Republican rival Mitt Romney campaigned in Ohio.
Obama had to show official identification to vote in Cook County although voters on Election Day will not have to do so at their home precincts, County Clerk David Orr said. Obama whipped out his Illinois driver's license, saying, "Now ignore the fact that there's no gray hair on that picture."
"I voted," Obama said as he finished up, becoming the first president ever to cast an in-person ballot before Election Day.
"For all of you who have not yet early voted, I just want everybody to see what an incredibly efficient process this was thanks to the outstanding folks who are at this particular polling place," Obama said. "Obviously folks in Illinois can take advantage of this. But all across the country we're seeing a lot of early voting.
"It means you don't have to figure out whether you need to take time off work, figure out how to pick up the kids and still cast a ballot. If something happens on election day you will have already taken care of it. If it's bad weather you won't get wet -- or in Chicago, snowy. But this was really convenient. I can't tell you who I voted for. But I very much appreciate everybody here. It's good to be home back in the neighborhood."
He then took pictures with those in the polling place before heading back to his limousine en route to the final stop of the day in Cleveland.
Obama took a red-eye flight aboard Air Force One from Las Vegas to his first stop of the day in Tampa, Fla. He also attended a rally in Richmond, Va., before heading for Chicago.
"My voice is getting a little hoarse. But I'm just going to keep on -- just going to keep on keeping on," Obama told supporters.
Rolling Stone Friday planned to publish an interview with Obama in which he described Romney with a barnyard epithet.
Douglas Brinkley, the history professor who wrote the magazine piece, told Politico as he and Rolling Stone Executive Editor Eric Bates left the Oval Office after a 45-minute interview earlier this month, Bates told the president his 6-year-old daughter wants Obama to stay in office.
"[S]he said, 'Tell him: You can do it,'" Brinkley recounted.
He said Obama grinned and responded: "You know, kids have good instincts. They look at the other guy and say, 'Well, that's a bull[expletive]er. I can tell.'"
Much of Obama's campaign rhetoric this week has centered on whether Romney can be trusted on both domestic and foreign policy, and coined the term "Romnesia" to describe what he says are his opponent's shifting positions.
Obama picked up the endorsement of former Republican Secretary of State Colin Powell, who also endorsed Obama in 2008. Obama campaign spokeswoman Jen Psaki said Powell had not advised the president or the campaign he would make the announcement on "CBS This Morning." She said the president called Powell to thank him for his support but there has been no discussion of any joint appearances.
The president also picked up the endorsement of The Washington Post.
Romney spoke to workers at Jet Machine in Cincinnati as he tried to woo the last of the undecided voters before the Nov. 6 balloting. Romney hit familiar themes: repealing the Affordable Care Act, jobs and the budget deficit as he picked up endorsements from The Wall Street Journal and The Detroit News.
Romney attended a rally at Defiance High School in Defiance with country music singers John Rich and Randy Owen.
"We're going to finally tackle the problems politicians have spoken about for years but haven't been willing to deal with. We're going to finally get America strong again with an economy to compete with anyone in the world," Romney said in an appearance at Worthington Industries in Worthington, Ohio. "We're going to help America get good jobs and rising take-home pay."
Romney is to travel to Iowa Friday before returning to Ohio to join running mate Paul Ryan in North Canton.