It wasn’t an earth shattering discovery in this case, but a digital newspaper search located a reference to Asa Landon on a list of post office letters in the Rockford, Illinois, post office on 1 January of 1850. This image comes from the Rockford Forum of 9 January 1850.
Asa is listed in the 1850 US Census for Winnebago County and he married in Winnebago County (and is listed as “of” there) in his 1849 marriage, so the listing of his name wasn’t a newsflash to me.
However, there are times where a person’s name on one of these lists can help show they were thought to have been in a certain location at a certain point in time. Remember that just because someone sent a letter to someone in a certain village doesn’t necessarily mean that that person was living there at the time of the “letter list.” It means that someone on the day they mailed the letter thought the person lived there–or at least hoped they did.