The replica 18th-century farmhouse at the Claude Moore Colonial Farm at Turkey Run in McLean, Va., was destroyed last week by fire. The farm has been a place to learn about the life of a poor tenant farm family in the 1770s. It is the only privately owned national park in the United States. Because of the use of the house and the layout, it was impossible to acquire insurance. The Friends of the Claude Moore Colonial Farm, a nonprofit educational organization, has begun a fund-raising campaign to rebuild the house. For information, call (703) 442-7557.