 While early forms of a mechanical mail sorter were developed and tested in the 1920s, the first sorting machine was put into operation in the 1950s.To handle rapidly growing mail volumes, the United States Postal Service installed the first semiautomatic sorting machine on April 10, 1957.The Transorma Letter Sorting Machine, manufactured by the Dutch company Werkspoor and distributed in the United States by Pitney Bowes, consisted of an upper and lower section, a conveyor belt transport and a series of five sorting keyboards.