Source: http://www.nytimes.com/interactive/2014/...

State and local police departments obtain some of their military-style equipment through a free Defense Department program created in the early 1990s. While the portion of their gear that comes from the program is relatively small (most of it is paid for by the departments or through federal grants), detailed data from the Pentagon illustrates how ubiquitous such equipment has become. Highlighted counties have received guns, grenade launchers, vehicles, night vision or body armor through the program since 2006.