Income inequality is a human rights issue (if you’re not convinced, go here or here first). Here are a few maps about income inequality in the U.S., in addition to some older posts on the same subject (see here, here, and here).
(source, click on the image to enlarge; a higher Gini value means more inequality)
You can clearly see the maps becoming darker over time, and also the shifting of inequality across the country.
However, if you take the global view and move away from the U.S., income inequality has actually gone down over time. See here. More maps on income inequality are here. Something on the related concept of relative poverty is here. And more human rights maps are here.