Treasure Island was acquired by the Philadelphia Council of the Boy Scouts of America in 1912, making it one of the first council-owned camps in the country.  It sits on an island in the middle of the Delaware River and is actually located in Kingswood Township, New Jersey.  Among other things it was the site of the founding of the Order of the Arrow, and the home of Lodge #1 - Unami.

For many years mail was taken by rowboat to Pipersville, PA for posting. Sometime in the early to mid 1930s a seasonal U.S. Post Office was established on the island and a postmaster was duly appointed.

A four-bar hand stamp was used for a postal mark until 1940 when a rotary cancellation first appeared.

For other U.S. Seasonal Boy Scout Camp Post Offices see:

• Kanowahke Lakes, New York
• Ten Mile River, New Jersey
• Owasippe, Michigan