You've been to 0% of these places
DLuvBaby's "The US National Park System Passport Stamps"
The US National Park System has a program called the Passport To Your National Parks. In this "passport" you may place "Stamps" for areas, regions and the nation. The sites are National Parks, National Historic sites, etc. They also have cancellations that you may put in your "Passport" showing the date you visited that site. It is unclear how many sites have a stamp while some sites have multiple stamps. See the list of cancellations in DLuvBaby's "The US National Park System Passport Cancellations." Please feel free to add to this list and if possible scan in an image of your stamps for the sites you add.