How has urbanization affected population distribution in the United States?

Populations of metropolitan areas have increased.

Urbanization caused many people to cluster into large cities. When a city was forming, many jobs began to open. People would leave their unstable farming, trading, fishing etc ... jobs in the rural areas for a more secure factory, office, business job opportunity in the city. This means that the population is distributed unevenly across the US, with the majority of people living in urban areas.