Out at our cabin in CO, that my grandpa built in the late 40's, there was a huge box in the garage. This box was full of OLD calendars. The trend of writing on the calendars didn't really start until early 60's or so, but it is still going on today.
Any way a few years ago I brought the box home and put all the writing on the computer. Basically it is a daily diary of the things done, places went, # of fish caught, that kind of stuff while there. Makes for some really neat reading, as there has now been 5 generations of my family that have used the cabin.
