JFK Was Here Gateway
Los Alamos, New Mexico
Officially titled the John F. Kennedy Memorial, it's actually a blocky gateway, painted yellow and green, with a big Kennedy-profile bronze medallion at the top and plaques on either side. It was built to commemorate a visit that JFK made in December 1962, the first by any President to this mountainous part of New Mexico.
According to the plaques, JFK gave a speech on the high school football field encouraging the people of Los Alamos to keep up the good work of building America's atomic bombs.