"The Four Hundred" list was a phrase coined by Ward McAllister, a rich New Yorker who thought that there were exactly 400 people in New York who mattered. This elite was strictly limited, in his opinion, which means that people within this circle held up to each other, disregarding the outside world and always trying to become better than the neighbor: they wanted to spend more, live in bigger homes, have more expensive cars, all in hope to better show off their top position on the social ladder.
