Final answer:
Prior to 1800, the underlying principal behind positioning was Central Place Theory.
Step-by-step explanation:
The underlying principal behind positioning prior to 1800 was Central Place Theory. In regions where no single location had special site location advantages, situation advantages became very important. This was particularly true in areas like the vast plains of the United States during the 1800s, where there were few navigable rivers, waterfalls, or ports. The concept of situation advantages led to a predictable geometric pattern of cities, towns, and villages in these areas.