The park is also believed to mark where Major Powell started his earlier expedition down the two rivers in 1869.

The park includes a stone marker commemorating the activities of John Wesley Powell.

He led exploratory expeditions into some of the most inhospitable parts of the American West, notably including the first documented descent of the Grand Canyon.

[3] These two expeditions are generally considered to have covered the last large land area in the continental United States left unexplored by European-Americans.

Today, the city of Green River marks the Powell expedition history with annual events.