The preceding studies allowed the central and northern parts of the country to be known. However, large areas of Patagonia remained unknown, not only from a geological but also from a geographical point of view. Francisco P. Moreno was an enthusiastic explorer of the southern regions from 1873 onwards. He carried out several expeditions to Patagonia, collecting numerous geological samples and fossils through the Argentine Scientific Society, which allowed him to initially create a modest museum in his own house. With the creation of the city of La Plata, he proposed a plan to build a museum on par with the new city, which was approved by the authorities. In 1884, the La Plata Natural Sciences Museum was built under his direction, which became a leading institution not only for Argentina but also on a continental level. With the collaboration of Florentino Ameghino, his paleontological collections were expanded, and through hired personnel, important expeditions to Patagonia were initiated. During those years, the German geologist Rodolfo Hauthal took charge of the museum’s Geology section, and Alcides Mercerat of the Paleontology section. The explorations were reinforced by the participation of Carl E. Burckhardt and Leo Wehrli, Swiss geologists who carried out research in the northern sector of the Patagonian Cordillera. In 1902, border problems with Chile led Francisco Moreno to take charge of the studies as an expert to collect the necessary information to establish the border on both sides of the Andes Mountains. The extensive studies carried out by a legion of topographers, naturalists, and geodesists made it possible to gather the necessary information to present at the arbitration, which implied a great advance in the geological knowledge of Patagonia.