Henry R.Palmer; This was Air Travel. Bonanza Books 1967
When the Post Office asked for bids on the Chicago-San Francisco route in 1927, Boeing won with the lowest bid. In 5 months they had modified a 1925 design and built 25 examples of the plane shown above, the big and rugged 40A. By mid year they had pioneered the first comprehensive air transport service in America. With a 400 hp Pratt and Whitney, the planes cruised at 110 mph while carrying a 1000 lb payload of mail and passengers. Seventy seven were built between 1925 and 1932. Three remain, one each at the Henry Ford Museum, The Museum of Science and Industry in Chicago and the sole flying example based at the Western Antique Aeroplane and Automobile museum in Hood River, Oregon.