I recently updated the Income Layer on Justice Map to use the latest 2011-2015 American Community Survey data.
You can view the data by county or by census tract (roughly 4000 people). While census tracts provide higher resolution that helps us identify areas of environmental injustice, unfortunately the confidence interval is much larger. So there is a lot of noise in the data. If you are looking at the income layer and see a random checkerboard of blue and red - that is noisy data.
As part of this process, I added a Income Change layer that shows the change in median household income between the first period (2006-2010) and a second period (2011-2015).
It is easiest to see the trend in changing income by looking at the counties. The census tract data is even noisier than the regular income data, as the confidence interval is approximately twice as large. However where there are strong trends - like gentrification in DC and Philadelphia you can easily see them at the tract level.