The Sierra Club is launching a five-year campaign to protect and restore millions of acres of wildlands along the route traveled nearly 200 years ago by the explorers Meriwether Lewis and William Clark. The group has its eye on 34 sites in eight states, mostly public land, that it would like to keep from development. Its ambitious proposals include designating free-flowing stretches of the Missouri River as “wild and scenic,” making Oregon’s Steens Mountain a national monument, and breaching four dams on the lower Snake River in Washington state. The National Park Service estimates that up to 25 million people will mark the bicentennial of Lewis and Clark’s 1804-1806 expedition by traveling along portions of the explorers’ route in the next five years. The Sierra Club hopes to channel some of the public excitement into a push for conservation.