Katherine Stinson, the first woman to fly official airmail, did so at the 1913 Montana State Fair Aviation Meet, September 22-27. She was sworn-in as an authorized mail agent and flew mail from a post office substation at the fair, held in Helena. On four days (September 23, 24, 26, and 27), Miss Stinson flew the mail around the fair grounds and dropped mail bags to waiting postal officials. Inclement weather prevented flights on September 22 and 25. She carried 1,333 pieces of mail during the four days. The Post Office Department designated the route as No. 663,002. Fewer than ten cards and covers are known today.
A large, bright pinkish-red, circular postmark cancels the 1-cent Washington stamp. The postmark reads, "AERO POST / SEP 24 1913 / HELENA, MONT." The sender wrote, "Dear Marie, From fair grounds to post office by aeroplane. Ed." The card is addressed to Miss Marie Fromueller, Great Falls, Montana, and appears to be signed by Stinson on the picture side.