Situated in southeastern Harford County and edged by the Chesapeake Bay and the Bush and Gunpowder Rivers, the U.S. Army bases known as Aberdeen Proving Ground, Edgewood Arsenal, and Fort Hoyle have been home to ordnance, chemical, technology, and artillery commands. The photographs in this volume include scenes of the fertile farmlands of Aberdeen, Edgewood, and Michaelsville, and their transformation, which began in 1917, into the military base known today as Aberdeen Proving Ground, or APG. Views of daily life on base include the "Toonerville" Trolley, a small-scale train that shuttled commuting personnel between the main gate and the buildings on post. The images document changes in the ways wars have been fought and changes in society as a result of war. Brave officers voluntarily tested the effects of mustard agent and other chemical weapons on protective clothing and gas masks. Local women sewed gas masks for troops and civilians. Women moved into key jobs on base during World War II, manufacturing and maintaining tanks and weapons systems as the need for great numbers of troops depleted the workforce of civilian males. APG scientists led the way into the computer age when they developed ENIAC, the first electronic digital computer.