In response to the request of Charles A. Lindbergh and to highlight the famous aviator's previous employment as an air mail pilot, the Post Office Department authorized Lindbergh to fly air mail over his prior assignment as a Contract Air Mail Route 2 pilot for two days: February 20 and 21, 1928. 

This cover was carried on the February 20, 1928 Contract Air Mail Route 2 flight from Springfield, Illinois to Chicago, Illinois (where it was backstamped) and is listed in the Contract Air Mail Flights (CAM) Section of The American Air Mail Catalogue as 2N9combination.

In 1929-1930 Robertson Aircraft Corporation was involved in a series of mergers, ultimately being absorbed by The Aviation Corporation, and operated under the name American Airlines.