This is a product of the Homeland Security Defense Mapping Project, which is intended to help law enforcement during a time of civil disaster or terrorism, that the federal government has spent billions on -- mostly culling information from the public domain.  It's designed to be disseminated widely -- so everybody from hick town police departments to the NYPD have access to the data they need in case of emergency. Ironically, most of the data comes from things like OpenStreetMap and the reports put out by government agencies. Very little is actually new work.

Is it really useful to first responders and worth the billions put in? That's a bit more debatable, as most of them have Google Maps on their phones which have most of the same data. But then again, that can be said about most defense spending -- maybe it's useful -- but I've never actually seen a terrorist at the grocery store or the gas station.