New York became the most populous urbanized area in the world in the early 1920s, overtaking London. The metropolitan area surpassed the 10 million mark in the early 1930s, becoming the first megacity in human history. The difficult years of the Great Depression saw the election of reformer Fiorello La Guardia as mayor and the fall of Tammany Hall after eighty years of political dominance.

In the early 1920s, what was the second most highly populated city in the world?