H.R.3408: To authorize the Secretary of the Interior to adjust the boundary of the Stephen Mather Wilderness and the North Cascades National Park in order to allow the rebuilding of a road outside of the floodplain while ensuring that there is no net loss of acreage to the Park or the Wilderness, and for other purposes.

Amends the Washington Park Wilderness Act of 1988 to authorize the Secretary of the Interior to adjust the boundaries of the North Cascades National Park and the Stephen Mather Wilderness in Washington state in order to provide a 100-foot wide corridor along which the Stehekin Valley Road may be rebuilt: (1) outside the flooplain between milepost 12.9 and 22.8; (2) within the boundaries of the Park; and (3) outside of the boundaries of the Wilderness.

Requires that the boundary adjustments be such that equal acreage amounts are exchanged between the Wilderness and the Park.