Almost everyone knows you got mail from AOL or zip code. Fewer know what Z.I.P. stands for. The more mature (older) among may know what R.F.D. (like Mayberry RFD) stood for.
Let's start with the oldest, RFD stood for Rural Free Delievery. At the turn of the 19th century, people who lived in the country had to pay someone to deliver their mail or go to the post office to pick it up. Most of the time, the post office was a long ways away. The postmaster general came up with the idea of free delivery for country (rural) areas. So R.F.D was born.
Zip code for mail is still around but what does it stand for? Zone Improvement Plan. The idea was to get mail to travel along more efficiently or ZIP along. In 1943 the post office started a system to speed along mail delivery. Only large cities recieved a 2 digit z.i.p. code. By the 60's, a more efficient way was needed so a 5 digit code was implemented. What was Detroit's 2 digit zip code?
Email has almost wipe out postal mail.( now called snail mail) You can now send a letter in seconds.There is much contoversy over the invention of electronic mail. It came about in the 70's.
Now go find the cache and see how it relates. It is on a hill a small hike from parking. Was it Detroit 10