What an interesting question. I pondered even further back to the days of Kit Carson sending a message to his investors as he blazed a trail to Oregon / California.
What I wonder is how much it cost to send a letter somewhere and how they selected which one to carry. I guess first it would be who knew someone else and where that was, the significance of the relationship - business, Love, and etc, and the importance of the information.
Does anyone remember the movie made in the 50's with Charlton Heston as Buffalo Bill? I wonder if the railroad followed the pony express routes and how they chose which route was best to follow. Trail blazers for sure as assuredly going between A → B was not always a straight line . . . hmmmm.
Thank you for the inspiration to ponder and maybe wander towards reading about its history Patty :-)