Ak-Sar-Ben Field, whose hangars stood on the southeastern corner of these grounds, was used extensively during the early development of the U.S. Postal Air Mail Service. Ray Benedict landed here with the first air mail from Chicago on May 15, 1920, and William DeWald piloted the return flight the same day. The Omaha-San Francisco leg of the transcontinental route was opened by Pilot Buck Hefron the following September. Daytime air mail service from New York to San Francisco began on September 8, 1920, and the first shipment from the east was flown into Omaha by James Murray. Although the early air mail flights took place during daylight hours, the feasibility of night flying was soon explored. On February 22, 1921, Jack Knight took off from the North Platte, Nebraska, airfield on the first night air mail flight in the United States. He landed here at Ak-Sar-Ben Field before continuing on to Chicago. The efforts of these pioneer aviators led to the inauguration, on July 1, 1924, of day-night air mail service from coast to coast. In September, 1974, the Air Mail Pioneers of America met in Omaha to observe the 50th Anniversary of this significant event in aviation history.