Forest County, Pennsylvania
Forest County is located in northwest Pennsylvania and is one of the least populous counties in the state. It was established in 1846 and was expanded to its present size in 1866. Its rural and remote nature coupled with its small population size makes it an interesting area to study. Detailed census data was downloaded and combined for the years 1870 to 1940 (excluding the 1890 census records which were destroyed in a fire) resulting in a database of over 47,000 records.
In the 1880s the population of Forest County nearly doubled as the railroads expanded and provided an outlet for the area's raw materials. The population peaked in 1900 then dropped by an average of 2,000 persons over the next three decades.
The chart below, developed with ggplot2 in R, has traditional box plots along with jitter plots showing the population of Forest County from 1870 to 1940. Notice the change in distributions for each census year as the County's population aged progressively over 70 years. The average age was always a year or two higher than the median age and went from 21.6 years in 1870 years to 30.9 years in 1940. Also, notice the outliers in the early census years. These ages were entirely with the fourth quartile in later years.
