"Those that cannot remember the past are condemned to repeat it."

This is from this site featuring photos of railways in Maryland, including the MARC commuter line where these posters are being displayed. "Those who cannot remember the past are condemned to repeat it. " --George Santayana (1863–1952), Spanish-born U.S. philosopher, poet. Life of Reason, 'Reason in Common Sense,' ch. 12 (1905-6). William L. Shirer made these words the epigraph for his Rise and Fall of the Third Reich (1959).