POPULATION AND POVERTY: By 2010, the census counted about 21,000 people in Ferguson, which is about 10 miles north of downtown St. Louis in the broader area known to locals as North County.

Robert Siegel talks with Dr. Colin Gordon, a history professor at the University of Iowa, about how the map of St. Louis County reveals some of the sources for the recent unrest in Ferguson, Mo.

POPULATION AND POVERTY: By 2010, the census counted about 21,000 people in Ferguson, which is about 10 miles north of downtown St. Louis in the broader area known to locals as North County.