The Aerial Screw
The word 'Helicopter' comes from the french word 'hélicoptère' which is derived from Greek, literally meaning 'spiral wing'. References to vertical flights date back to 400 BC but it was Leonardo da Vinci's design of an aerial screw in the 1480s that was the first record of advancement towards vertical flight.
Pioneer of aviation, Alphonse Penaud, developed model helicopter toys in 1870 and these in fact inspired the Wright Brothers to pursue their dream of flight.
However, it wasn't until 13 November 1907 that french inventor Paul Cornu managed to lift to 1ft off the ground for 20 seconds in his Cornu helicopter. This was reported to be the first truly free flight with pilot. Various other experimentations took place after Cornu's vertical lift off but it wasn't until the 1920s that early development of helicopters really took off.
This image is actually ground testing of the de Bothezat quadrotor helicopter at McCook Field in 1921.