This website is interesting!
www.cdn-money.com
You enter the serial numbers of your money and if you’re lucky someone else has entered the same serial numbers, and you can see where the money was before it came to you, and when!
I found out about the site one day the $20 bill I got had the website stamped on. For any old unstamped bill, it’s pretty unlikely you’ll get a hit, but I think it’s worth trying. You can get a user name and keep track of bills.
If you’re not keen on entering your money’s serial numbers, you can look at the paths of the bills with the most ‘hits’. It’s strange how some bills manage to fly across the country while others stay in the same place for months.