Research Brief

2020 data obtained via U.S. Census Bureau
Historic data obtained via IPUMS NHGIS
Last Updated: 04/26/2021

Historic Population Change in Pennsylvania: 1900 to 2010


The year 2020 marked the 24th decade in which the census has been conducted for the United States and its territories, a tradition that started in 1790. As we the final 2020 Census data are released, for now just nation and state, let us explore how much has changed since the start of the last century. [Note: Sections referencing county data will be updated as final 2020 Census data are released].


Statewide Historic Growth

Pennsylvania started out the 20th century with a population just over 6.3 million [Figure 1] and ranked second in the U.S. based on population size. Pennsylvania’s growth was highest in the first few decades as well, growing by 1.3 million from 1900 to 1910, 1.0 million from 1910 to 1920, and just over 0.9 million from 1920 to 1930 [Figure 2].


By 1950 Pennsylvania’s population broke 10.0 million, despite slowed growth from 1930 to 1940 during the Great Depression and a minimal rebound from 1940 to 1950. Pennsylvania was also dethroned as the second largest state in 1950 by California, falling to third largest.


Pennsylvania added over 820,000 persons between 1950 and 1960, close to its pre-Depression growth, but growth declined again during the 1960s and came to a near standstill during the 1970s and 1980s. As a result, Pennsylvania’s rank among other states fell to fourth largest in 1980 and fifth largest in 1990, displaced by Texas and Florida, respectively.


A minor resurgence in growth during the 1990s and 2000s put Pennsylvania’s population at 12,702,379 as of 2010 - double the population size of the Commonwealth in 1900 – making it the sixth-largest state by population size after Illinois. The most current population estimates put Pennsylvania back ahead of Illinois, but we’ll have to wait until the 2020 count is released to know for sure.


Regions of Pennsylvania

We separated Pennsylvania into six regions to identify trends in growth by region from 1900 to 2010 [Figure 3]. Our regions for this analysis include South Western Pennsylvania (SWPA), Northern Pennsylvania (NPA), Central Pennsylvania (CPA), South Central Pennsylvania (SCPA), Northeastern Pennsylvania (NEPA), and Southeastern Pennsylvania (SEPA). Regions were constructed based on geographic proximity and similar patterns of growth.


Historic Growth by Region

Southeastern Pennsylvania (SEPA) began the 20th century with a population of just over 2.0 million in 1900, followed by Southwestern Pennsylvania (SWPA) at 1.4 million [Figure 4]. The remaining regions of Pennsylvania had populations ranging from the 600,000 (SCPA) and 770,000 (CPA) in 1900. By population size, the regions ranked 1) Southeastern PA, 2) Southwestern PA, 3) Central PA, 4) Northeastern PA, 5) Northern PA, 6) South Central PA in 1900.


Southwestern Pennsylvania (SWPA) was the fastest growing region in Pennsylvania at the start of the 20th century having grown 35.0 percent from 1900 to 1910 [Figure 5]. The greater Pittsburgh area experienced a steep decline in its rate of growth over the following decades, eventually experiencing a population decrease in the 1960s that would continue through 2010.


Northern Pennsylvania (NPA) had a somewhat consistent rate of growth between 4.0 and 6.0 percent until the 1980s which marked a decrease in population for the northern portion of the state. In addition to Southwestern Pennsylvania, Northern Pennsylvania was the only region that ended 2010 with a population decrease.


Central Pennsylvania (CPA) experienced flat-lining growth from the start of the 20th century until the 1960s when it hit a low of just 0.2 percent. Central Pennsylvania had a slight resurgence in the 1970s, a small decrease in the 1980s, and then minimal growth through 2010.


Northeastern Pennsylvania (NEPA) had the most dramatic shift in population change during the 20th century. Having increased by over 25.0% from 1900 to 1910, the rate fell to just 10.0% for the following two decades and then population decrease starting in the 1930s that hit rates near -10.0 percent during the 1950s and 1960s. Since then, the region has steadily seen an increase in population growth due to development in counties on the New York and New Jersey border (Monroe, Pike, and Wayne).


The southeastern region of the state (SEPA) experienced quite a few ups and downs during the 20th century. Southeastern Pennsylvania started the century with a growth of roughly 20.0 percent from 1900 to 1910 slowed during the 1930s to about 2.0 percent. By the 1950s the region was growing again by over 13.0 percent. After losing population during the 1970s, the region grew steadily through 2010 at an increasing rate.


South Central Pennsylvania (SCPA) is the only region that has continuously grown since the start of the 20th century and has been the fastest growing region since the 1930s. The region began and ended the century with a growth rate hovering near 10.0 percent, experiencing a slight slowing during the 1910s and 1930s and a surge in the 1950s.


Despite being the smallest region by population at the start of the 20th century, SCPA was the third-largest region of Pennsylvania by 2010. By population size, the regions ranked 1) Southeastern PA, 2) Southwestern PA, 3) South Central PA, 4) Central PA, 5) Northeastern PA, 6) Northern PA in 2010.


Historic Population Change in PA Counties

How did population change in the past century at the county level? Table 1 reports the population of each county from 1900 through 2010 while Figure 6 will allow you to visualize a single county's growth trend. Share charts or download their underlying data using the toolbar across the top of each figure/table. Happy exploring!


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