 In 1949 the network extended from Cincinnati and Louisville east to Norfolk and points south.The map reached Knoxville in 1951-52, Columbus OH and Washington DC in 1955, Atlanta and Baltimore in 1962, New York La Guardia in 1966, Nashville and Memphis in 1968 and Chicago Midway in December 1969.In 1978, still under U.S. route regulation, Piedmont added Boston, Denver and Miami.