Being located between the Great Lakes and the Ohio River which served as the two major migration routes to the West, Mid-Western Pennsylvania has been viewed by various historians as a region whose settlement was delayed and growth retarded due to this isolation. This study analyzes the geographic, economic, political, and ethnological factors which influenced original settlement and the population's growth through 1860.The study reviews events of the second half of the eighteenth century when the region became the focus of intense strategic, commercial and political rivalries. The forces vying for domination of the area were in sequential order: The Iroquois Confederacy and the Erie nation, the French fur traders and the English fur traders, the French Empire and the English Empire, the American colonies in revolt and the British Empire and finally the newly independent states of Pennsylvania and Virginia.With the rivalries resolved and the sovereignty of Pennsylvania verified, the struggle between land speculators and pioneer farmers for easy access to control of the lands in the region became a paramount issue after 1790. The study analyzes the three land distribution schemes devised by the state of Pennsylvania and the confusion which their application.Despite the isolation of the region, its geographic limitations, uncertainty over sovereignty, and confusion with land titles, a quantitative measurement of population growth and density in the study area indicates that growth did not languish as severely as many secondary sources imply. Using the remainder of Pennsylvania, Ohio and the Northwest Territory for purposes of comparison in both growth and density, it appears that in both categories Mid-Western Pennsylvania's advancement did not differ radically from the regions which surrounded it.The essence of the study is a profile of the population in the Mid-Western Pennsylvania counties of Armstrong, Butler, Clarion, Lawrence, Mercer, and Venango based upon personal data recorded in the manuscripts of the census returns of 1860. To accomplish this 180,486 individuals living in the region were codified for computer use in the following five categories: county of residence, age group, sex, property holdings, and state or foreign nation of their birth. While compendiums published by the United States Bureau of the Census contain totals of each recorded category, this study by utilizing computer techniques shows the interrelationships between each of the categories. From tables contained in chapter six of the study it is thus possible to determine exactly how many persons of a precise sex, age group, level of property holding, and state or foreign nation of birth were residing in the region in 1860. The appendix contains the same data for each individual county of the region.Among the more general conclusions that can be drawn from the population data is the overwhelming predominance of the age group under twenty years old, and the slightly higher incidence of males in the population especially among those over the age of fifty. It is also evident that the population of the region was more static and insular by 1860 than the national norms. Among those whose nativities were from other states it is clear that migrants tended to move from the states immediately adjacent to the borders of Pennsylvania regardless of the direction. There is also evidence of a slight reverse migration of persons from states farther west returning to Pennsylvania. The ethnic composition of the population shows consistency from the earliest settlers through 1860. Scots-Irish and Germans in that order dominated the earliest settlement. By 1860 they continued to prevail, but the Scots-Irish had dropped slightly behind the Germans in numbers.The analysis of property holding follows predictable lines in that real property was far more prevalent than personal property, it was controlled chiefly by males, and concentrated among the older age groups. No discernable trend was apparent between the level of property holding and the state or foreign nation of birth. It appears from the study that economic opportunity must have been fairly equal in the region, or at least not based upon one's ethnic origins.The study concludes that the natural and historic forces affecting the region have molded it into a cultural transition zone which harbors a variety of characteristics of the regions which surround it, but where none of the criteria used to classify those regions are dominant. What ever the classification indices selected, topography, economy, culture, or ethnography, Mid-Western Pennsylvania's chief distinctiveness is in its diversity.