6. The Holland Tunnel is a National Historical Landmark
New Jersey entrance. Image via The Library of Congress.
The Holland Tunnel was named a National Historic Civil and Mechanical Engineering Landmark by the American Society of Civil and Mechanical Engineers in 1984 and a National Historic Landmark by the U.S. Department of the Interior in 1993. The designations were predominantly for its groundbreaking ventilation system. When designated as a National landmark, it became the sixth tunnel in the country with the distinction.