Wild Sky Wilderness and Backcountry Wilderness Management Area Act of 2004

Wild Sky Wilderness and Backcountry Wilderness Management Area Act of 2004 - Designates specified Federal lands in the State of Washington (the State) as: (1) the Wild Sky Wilderness (the Wilderness); and (2) the Skykomish Backcountry Wilderness Management Area (the Area).

Directs the Secretary of Agriculture to manage the Wilderness in accordance with the Wilderness Act and this Act. Authorizes the Secretary to use helicopter access to construct and maintain a joint U.S. Forest Service and Snohomish County repeater site, in compliance with a Forest Service-approved communications site plan, to improve communication for safety, health, and emergency services.

Directs the Secretary to: (1) develop a management plan for the Area (but prohibits the Secretary from permitting commercial timber harvest in the Area); (2) establish a trail plain for specified National Forest System lands to develop a system of hiking and equestrian trails in the Wilderness and the Area, and trails adjacent to the Wilderness or the Area; and (3) carry out a land exchange with the Chelan County Public Utility District in the State, subject to specified requirements.