Looking at the demographics of households with less than $30,000 a year in income, it appears they are mostly headed by retired people. As Visualizing Economics notes [3], households with incomes below $30,000 are more likely to be located in rural and urban areas than the national average...
[4]
and looking at the the poverty rate by county, very low income households (under $23,000 for a family of four) are concentrated in places like Mississippi, Texas, and South Dakota.
[5]
Charts: Visualizing Economics [3] [3]