Take your pick. Many can be mentioned. Many can be argued and justified. I think it's close between the Wright Brothers historic first flight in Kill Devil Hills, North Carolina and the landing on the moon. The Wright Brothers achieved in 1903 what no one else could do before them and what eventually turned into commercial air travel, aerial weapons of war and the space program. The landing on the moon was a "middle finger" to the Russian space program that was kicking our butts early on and just the sheer magnitude of men walking around on a surface other than our earth was pretty damn amazing for 1969. By the way, no other country has done it since.