This was flown on the first north bound flight from Richmond, Virginia to New York City on Contract Air Mail (CAM) Route number 19. This was one of the 16 legs of service between Atlanta and New York City and the cities in between that occurred on May 1 - 2, 1928It was interesting in that the many legs of this first flight. There are a number of varieties of most of the legs making a total of 46 covers to have a full set. Some legs and varieties are more rare than others, this one is one of the most common. It is American Airmail Catalog number 19N4 and has a catalog value of $5 but you can find this one for less. The airline that flew this first flight was Pitcairn Aviation and an interesting aspect is these legs were the first time overnight air mail service was regularly offered for US mail.
If anyone is interested in collecting first flight covers the best place to start is to join the American Air Mail Society at
http://www.americanairmailsociety.org/ You get a really nice small monthly magazine on old first flight covers, discounts on airmail catalogs, and access to major experts.