The above image depicts an Army air raid detection station set up in Green-Wood Cemetery in January 1941. In the years leading up to World War II, as there was an increased fear of air attacks, the United States developed and employed a system to monitor the sky for enemy aircrafts. Stations were set up that incorporated the use of searchlights and sound and heat locators. This view in Green-Wood shows a group of soldiers monitoring sound locators for the noise of airplane engines. Green-Wood’s high-elevation and proximity to urban centers made it an ideal location for the station. Click the image to expand.