The original XR-1 helicopter, first flown tethered as early as 12 May 1941. The water tower reads General Steel Castings, proof that this is the Platt-LePage factory site in Eddystone. Several early American helicopter companies were based in Pennsylvania, including Piasecki, and today Boeing's helicopter factory occupies the General Steel Castings site, across the Crum Creek from the Platt-LePage site. Photo from: Vertical Flight Society

Preceded by the XR-1, the XR-1A first flew in May 1943 and crashed on 26 October 1944. Photo from: Vertical Flight Society

First flown on 12 May 1941, the Platt-LePage XR-1 (PL-3) was the first helicopter ordered by the US Army. Laurence LePage studied the Focke-Wulf Fw 61 in Germany. Two examples of the XR-1 were built, this being the modified XR-1A. The larger PL-9 design became the McDonnell XHJD Whirlaway. Frank Piasecki worked at Platt-LePage as a young engineer. The photo comes from the files of the US Army's Watertown Arsenal, Massachusetts. Photo from: National Archives at Boston