The American Poor

I was combing back through what I've missed at EconLog a few days ago, and I found this post. The post itself isn't what interested me, though - look through the comments. You'll see a debate concerning who the poor are in America. I'm very curious as to what everyone else thinks. What groups of people comprise today's poor? Do they have certain distinguishing characteristics (i.e. single mother, high school dropouts, etc.)?