In this chapter, the historical background of the archaeology in the Pampas and Patagonia is discussed and summarized. It encompasses a period of about 100 years, between the 1870s when the first archaeological investigations took place in the Pampas and Patagonia (Ameghino 1880–1881; Holmberg 1884; Moreno 1874; Moseley 1892; Zeballos and Pico 1878) and the late 1970s when there was a theoretical and methodological shift in the archaeology of both regions, which gave rise to modern research. The current regional models in the Pampas and Patagonia are a product of this last period’s research, first with a processual orientation and then adding other theoretical approaches (evolutionary, processual-plus/neo-processualism, post-processualism, etc.). However, some of the data and ideas generated in this first 100 years of investigation are still present in contemporary debates, as shown in the following chapters of this book.