I have my mom to thank for that.
Check out this product:
It's called the My Scratch Map from IWOOT . It's a nifty way to document where you've been.
Step 1: Travel
Step 2: Scratch off where you've been on your handy map!
Easy peasy. Too bad it doesn't include the individual states, though. Maybe a fun gift for a kid?
I'm still holding out for my jumbo-sized world wall mural though.