Changes to the U.S. Population Over Time

Instructor: Dr. Douglas Hawks

Douglas has two master's degrees (MPA & MBA) and a PhD in Higher Education Administration.

According to the U.S. Census the population of the U.S. has grown from about 4 million to about 320 million in 2015, but that's not the whole story. In this lesson we'll learn the cause of that growth and how demographics have changed over the same time.

Changes to the U.S. Population Over Time

Before we jump into interpreting statistics and trends, it's important to set the parameters of our discussion. Since the title of the lesson is 'Changes to the U.S. Population over Time,' we aren't going to talk about the population of the North American continent prior to 1789. We are using the year 1789 because that's when the U.S. Constitution was ratified, officially establishing the United States, and the first census was taken a year later.

Just the Numbers

If we just look at the numbers, the growth in the United States is impressive. Growing from 4 million to 320 million is an increase of 80 times and has made the U.S. the world's 3rd most populous country. Much of that growth came from existing Americans having large families and a large part came from immigrants. Looking at the chart clearly shows that once the population hit 50 million around 1880, growth began to increase at a faster rate.

US Population Since 1790

It look 90 years for the population to of the United States to hit 50 million. The next 50 million only took a little under 40 years - half the time for the same amount of growth. That trend continued as it only took about 30 years for the next 50 million, 20 years for the next 50, and matched that rate over the last 20 years, increasing from 250 million to about 310 million since 1990.

The 20th century (1900-1999) was a period of exponential growth for the United States, averaging close to 4% per year. As of the latest census - 2010 - the annual growth rate in the U.S. was down to less than 1% at about .77%.

Demographic Changes

The number of citizens in the United States isn't the only change that has occurred over the last 225 years. Looking back at the chart of the growth, you can see that the growth has been more in a couple regions than in the others. Specifically, around 1940, the south and west started to grow at a faster rate than the north and the east. Any ideas why?

Think of what changes the American landscape was experiencing for the few years before 1940 that could lead to that growth. In the decades before 1940, both the cross-country train route was finished and the automobile was invented. Also, roads weren't something handled by the government until 1916, and even then they didn't really connect states like they do now until the late 1940s and early 1960s.

While the population centers around the turn of the 20th century were in the north and east - New York, Philadelphia, and Chicago - once transportation made it possible to move easier and industry began to boom on the west coast and in the southern states, the mass migration from cities to new areas began.

US Population Distribution

Diversity of Population Growth

It was during the 1850 census count that the ethnic background of people was asked. Prior to that, there was an entry for 'slaves,' but it didn't stipulate race. In 1850, there were just over 2 million immigrants and just over 20 million people, meaning 10% of the country were immigrants. You might think that number grew exponentially, much like the total population, but new legislation limiting immigration was passed in the early-1920s and then with World War II and the Great Depression, immigration slowed dramatically.

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