The White House today released an interactive map of excess properties maintained by the federal government. And, even better, it appears they made it with open-source tools. An explainer: 

The Federal Government is the biggest property owner in the United States, and billions of taxpayer dollars are wasted each year on government properties that are no longer needed…. There are roughly 14,000 buildings and structures currently designated as excess and thousands of others that are underutilized. These properties range from sheds to underutilized office buildings and empty warehouses. Over 7,000 of these properties are plotted on this map, zoom in to see Excess Properties in your state and around the country.

You can zoom into a state or specific property and also download the data set. In this view, proportional symbols represent excess properties:

Got to interactive version | Built with MapBox and OpenStreetMap