This is a big job! If you know of a walk across a country, or have done one, let me know so it can be shared!
For some countries, e.g. USA and Western Europe, there are numerous accounts easily accessible so I’m not listing them at this stage. So if you decide to pull a Forrest Gump, it’s not hard to find reports on your own.
I have done my best to find the original material by the author. Sometimes this might just be a link to a book on Amazon. Further exploring will uncover more material. Other links go to press articles.