Ahuge crowd of vietnamese gathered outside the in saigon, hoping to be evacuated and making for a chaotic scene.

It was the U.S. Embassy. Following the withdrawal of U.S. troops from South Vietnam, many of its fled to the embassy in the hopes to escape before the North Vietnamese Army arrives at the capital in Saigon.  Many either fled by plane or traveled to the boarder in Thailand to escape.

the us constitution is a living document, meaning that it can be changed over time as the country changes.