More than 13 million families in 2004 were unable at times to buy the food they needed, according to the U.S. Department of Agriculture. Finances are so strained for 5 million of those families that one or more members goes hungry as a result.

In An Atlas of Poverty in America, Penn State University economic geographer Amy Glasmeier takes a historical and contemporary look at the problems faced by the country’s poor. In an interview with Vikki Valentine of National Public Radio, she discusses the phenomenon of hunger in America.