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.
The coal miners' battle for dignity led to the largest armed insurrection since the American Civil War.
The most daring and innovative accomplishment at the turn of the 20th century.
The contradictory history of a dam that became a statement of American power and prestige.
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.