John Wesley Powell's epic journey into the unknown Grand Canyon was filled with adventure as his team mapped the Colorado River for the first time.
In 1934, American polar explorer Richard Byrd became the first to experience winter in Antarctica's interior.
Her 1963 warnings about the effects of pesticides and herbicides sparked a revolution in environmental policy.
High on a granite cliff in South Dakota's Black Hills tower the huge carved faces of four American presidents: George Washington, Thomas Jefferson, Abraham Lincoln, and Theodore Roosevelt.
The New Deal program CCC put three million young men to work in camps across America.
The American effort to relieve starvation in Soviet Russia in 1921 during the worst natural disaster in Europe in 500 years.
In 1927, the Mississippi River flooded from New Orleans to Illinois, leaving a million people homeless and leading to a major black migration to the North.
Vivid memories of those trapped in the terrifying temblor of 1906 that killed thousands of Californians.