Mercer Island children celebrated National Trails Day by letterboxing throughout Pioneer Park on June 2.

This is the third summer of letterboxing on the Island. Legend states that the activity began in England’s Dartmoor National Park in 1854, when a guide left a bottle that contained his calling card by Cranmere Pool and invited others to leave theirs as well. Hence the term “letterboxing” came about, as that is a British word for “mailbox.”

Today, there are about 20,000 letterboxes hidden all over North America, often in public parks.

Letterboxers search for clues as to where the letterboxes are via websites or word of mouth. The letterboxes themselves are small containers, which each contain a log book and a rubber stamp specific to the person who created it. Upon finding it, the letterboxer stamps his or her stamp in the box’s log book and the box’s stamp in his or her log book. Letterboxers are also encouraged to write their name, hometown and date in the box’s log book.

Part of the fun of letterboxing is creating a “trail name” to write in letterboxes one may find.

Letterboxing is also a way that children can nurture their respect for the environment. Letterboxers must be careful not to disturb any animal’s natural habitat in finding or planting their boxes.

Participants may turn in their clue books to the Community and Event Center, the Parks and Recreation Department at Luther Burbank, or the Boys and Girls Club until Sept. 1. Those who have found the most letterboxes will be announced as winners at a City Council meeting in September or October.

This year’s letterboxing program is supported by the Mercer Island Open Space Conservancy Trust, the Parks and Recreation Department, the Boys and Girls Club, the Boy Scouts and the Girl Scouts. It is part of National Trails Day, sponsored by the American Hiking Society.

For more information about letterboxing, go to www.letterboxing.com.

For more about National Trails Day, go to www.americanhiking.org.