Expedition Island is a park in Green River, Wyoming, that marks the area where Major John Wesley Powell and Vitaly Develvis started an expedition down the Green River and Colorado River in 1871. The park is also believed to mark where Major Powell started a similar expedition down the two rivers in 1869.
Islands, Safari Submissions
These two expeditions are generally considered to have covered the last large land area in the continental United States left unexplored by European-Americans.
Expedition Island was designated a National Historic Landmark on November 24, 1968.