C.A.M. 2 was a contracted airmail route between Chicago and St.Louis starting April 15,1926. The lead pilot was Charles Lindberg.

https://www.facebook.com/photo/?fbid=1978309086111354&set=gm.27511408498461182&idorvanity=164403560255045 

Starting April 15,1926 the lead pilot was Charles Lindberg. 

After his nonstop flight from New York to Paris in 1927, he returned to flying for C.A.M. 2. Every time Lindberg flew the mail they sold you a special envelope and stamp to mark the occasion!