Michelle and their youngest daughter, 9-year-old Sasha, are Spain. Malia is away at summer camp.
Despite official White House reports that he would spend the evening at home, Obama dined at a River North restaurant.
It is the president's fourth visit home since he was inaugurated in January of 2009.
Obama invited three of his best friends to his house on Greenwood Avenue in the Kenwood neighborhood Wednesday night. But everyone left soon after they arrived.
The presidential motorcade, waved on by well wishers along the route, arrived in the 5000-block of South Greenwood shortly before 6 p.m. A half hour later, University of Chicago Hospital vice president Dr. Eric Whitaker walked in and senior advisor Valerie Jarrett was a passenger in one of the black SUVs allowed inside. Then a few minutes past 7 p.m., the presidential motorcade suddenly left the president's home and headed downtown to the Graham Elliot restaurant in River North where Obama would eat his 49th birthday dinner.
"There is a lot of security there now. We got there before President Obama arrived so we got a glimpse of him as he was entering the restaurant," said Allen Yi.
"I was floored. I had to do a double take. I wasn't sure if it was him or not...it was great, a special night," said Mary Kim.
With Michelle and Sasha in Spain and daughter Malia at camp, the only family member to accompany the president is Bo, the first family's puppy. Neighbor James Nau and his dog Stanley understand why the president would bring the dog home as often as possible.
"The house in Washington is probably pretty nice, but you got to get the dog used to fact that this is where home is," said Nau.
On Thursday morning, the president will tour the revived Ford plant on Chicago's South Side where 1,200 workers will be hired to build energy efficient SUVs. In the afternoon, the president will lead a fundraiser for candidate for U.S. Senate Alexi Giannoulias and later two small events for Democratic candidates in general.
The next 24 hours could be particularly unnerving for the president and his advisors since the Rod Blagojevich jury is still deliberating and could return a verdict while President Obama is in Chicago. Those political advisors don't want that to distract from what the president wants to accomplish on this visit politically.