Most Densely Populated US States

Paterson, one of the largest cities in New Jersey, attracts internationally diverse pool of immigrants.
Paterson, one of the largest cities in New Jersey, attracts internationally diverse pool of immigrants.
  • The three most densely populated US states are New Jersey, Rhode Island, and Massachusetts.
  • Unique characteristics and drivers impact an area's population density, along with general factors.
  • There are numerous ways to measure population density.

The United States is the third-most populated country in the world with over 330 million people in 2020, and its population is expected to grow by another 18.5 million in just the next ten years. Clearly, the country will be seeing an increase in population density in many states. What are the densest US states today?

The most densely populated state (if we discount Washington, DC) is New Jersey. Rhode Island comes in second, and third on the list is Massachusetts. Puerto Rico is more densely populated than Rhode Island at 1,088 persons per square mile, but it is a US territory and not a state, so for the purposes of this article, it will be omitted.

Why are these states so densely populated?

Various factors impact whether an area will be densely or sparsely populated, such as a large population in a small land area. Locations with flat and low land, plenty of resources, along with temperate climates for growing crops will often have dense populations. As well, you will often find a high population density where there are good employment opportunities, especially in larger cities. Stable governments and communities with a desire to live in close proximity for security reasons are other contributing factors to dense populations. 

Beachgoers in Asbury Park, New Jersey, US. New jersey is the state with the biggest population density. Image credit: Sky Cinema/Shutterstock

These things apply to each of the three most densely populated US states but, more specifically:

  • The many jobs in New Jersey have contributed to its dense population. For instance, the state is home to a large portion of the pharmaceutical industry and its related jobs. Plus, New Jersey residents commute to New York City and enjoy a lower cost of living.
  • Historically, Rhode Island's large involvement in the slave trade, the Industrial Revolution, and fishing contributed to its high population density. Today, the state's growth results from its economy of healthcare, education, and manufacturing. 
  • The population density of Massachusetts is high in part due to its population increase of 5% during the past 10 years. The cause of this has been international immigration. People from all over the world are attracted to the state because of its strong economic, social, political, and cultural characteristics.
  • Though it is not a state, Washington, DC is even more densely populated than New Jersey, partly due to its small land area. In DC, regular government spending and growth in linked sectors like defense, technology, media, and lobbying and advocacy have provided the region with a strong economy. As well, millennials are increasingly looking to live in urban areas and the expansion of public transit has attracted many young people to this area.

Keep in mind, there is a difference between human population density and overpopulation. Overpopulation happens when the capacity of the environment to support the population is exceeded. 

Urban sprawl near Dallas, Texas. Image credit: Trong Nguyen/Shutterstock

Ways to measure population

The simplest way to measure human population density is by using a method called arithmetic density. This is the number of people living in an area, usually per square mile, of a city, state, country, or the world.

Other methods used to measure the density of human populations include:

Ecological optimum: this refers to the human population's ability to maintain its maximum size while everyone's living standards remain optimal.

Urban density: urban planners and designers use this term to describe the number of people living in an urbanized area, and they consider it important in learning about how cities operate.

Residential density: this is how much residential development can take place on a specific piece of land. The larger the units allowed per acre, the higher the density of the area.

Agricultural density: this is the number of farmers per unit area of usable land. The quality of an area's land is a large contributor to its agricultural density.

Physiological density: this is similar to agricultural density but it refers to the number of people per unit area of usable land.

Knowing that the three most densely populated US states are New Jersey, Rhode Island, and Massachusetts (along with, unofficially, Washington, DC and Puerto Rico), only goes so far, so it helps to understand the reasons behind this. Each state has its own specific characteristics and drivers, but there are general factors at play, too. Factoring the size of the land area, its relief, resources available, and the type of climate affect population density quite a bit. Finally, knowing how population density is measured can help to understand what these statistics mean.

Most Densely Populated US States

RankStateArea in square milesPopulation per square mile in 2019
1Washington DC6811,569.70
2New Jersey7,3541,207.80
3Rhode Island1,0341,024.50
8New York47,126412.8
16North Carolina48,618215.7
20South Carolina30,061171.2
22New Hampshire8,953151.9

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