The president's visit comes a day after returning from a six-day European tour of Ireland, England, France and Poland.
After days of focusing on the U.S. relationship with the rest of the world, Obama turned to an even more critical connection: his own, with the American people.
A monster storm tore through Joplin a week ago leaving more than 130 dead and hundreds more injured.
The president toured destroyed neighborhoods in the city of 50,000 in southwestern Missouri, and spoke at a memorial service held by local clergy and Gov. Jay Nixon for those who lost their lives.
He said it's impossible to know when or why such devastation strikes. But he praised neighbors for helping each other at great risk to themselves. He said there are heroes "around us all the time."
Sunday, officials announced the number of those unaccounted for dropped to 40 because of the latest deceased whose next-of-kin have been notified. The number had stood at about 100.
The tornado - an EF-5 packing 200 mph winds - injured more than 900 people. Tallying and identifying the dead and the missing has proven a complex and sometimes confusing exercise for authorities and loved ones.
The Associated Press contributed to this story