from the United States Lighthouse Society (USLHS) webpage . . .

The United States Lighthouse Society sponsors a Passport Program. A passport with a blue vinyl cover, similar in appearance to an official United States passport, is available through the Society and lighthouse retailers across the U.S. When you visit a participating lighthouse, you can get your passport stamped.

There are four panels on each page of the passport and each panel should have a different lighthouse stamp. When your passport is filled it will contain 60 stamps.

The stamps, designed by Society graphic designer Rusty Nelson, are a work of art. However, if you visit a lighthouse that is not participating in the program, is closed, or for whatever reason, you can’t get your passport stamped . . . take a picture of the lighthouse or cut out a logo of the lighthouse from a brochure and paste it in the square, or if you’re artistic, draw it in. When your passport is filled, send it to our office for verification (include $4.60 to cover Priority return mail postage).

There are four levels of accomplishment in the U.S. Lighthouse Society Passport Program. Each level is reached by completing a passport book & sending it to the USLHS Passport Fulfillment Service for verification. Upon achieving each of the four levels, you will receive an official, collectible patch recognizing your achievement and dedication to lighthouse preservation.

See more here.