The Semiquincentennial Commission, established to plan the observance of the 250th anniversary of the United States, includes several non-voting ex officio members. These members typically represent various federal agencies and organizations involved in the planning and execution of the anniversary events.

As of the latest information, the non-voting ex officio members include:

1. The Secretary of the Interior - This position is crucial as the Department of the Interior manages many historical sites and national parks.
2. The Secretary of Education - This member can help integrate educational initiatives related to the anniversary.
3. The Secretary of Defense - Involvement from the Department of Defense can provide a military perspective on the historical significance of the events.
4. The Administrator of the National Archives and Records Administration - This role is important for preserving historical documents and artifacts.
5. The Chair of the National Endowment for the Humanities - This position can help promote cultural and historical programs related to the anniversary.
6. The Chair of the National Endowment for the Arts - This member can support artistic initiatives that celebrate the anniversary.

These ex officio members play a vital role in ensuring that the commission's activities are aligned with federal resources and initiatives. For the most current and detailed information, you may refer to the official Semiquincentennial Commission website or related government publications.