Hydro-Aeroplane flight cover
In 1911 Hugh Robinson (1881-1963) was contracted to fly mail from Minneapolis, along the Mississippi River, south to New Orleans. A lack of financial assistance meant that the flight only went as far as Rock Island, Illinois. Anticipating Robinson's departure, clerks postmarked mail in Minneapolis from October 11-17, 1911. Robinson departed on the October 17, heading south along the Mississippi. He reached Prairie du Chien, Wisconsin, on the 19th, and this cover was off-loaded and delivered to the addressee.
Robinson carried between six and eight hundred pieces of mail on at least one segment of the flight. However, only about ten pieces have survived, this cover being one of them. All flown mail bears the handwritten description "Care Aviator Robinson, Hydro-Aeroplane Route" or something similar. The post offices along this route used no special postmarks, but some used various rubber stamp markings.
Robinson's flight proved the viability of airmail transport as early as 1911. It was not until 1918, however, that the Post Office Department established a regular route, that being from Washington to Philadelphia to New York.