Greetings, a Chilean speaks to you, the reason why our country is so long is basically because of our geography. the Andes mountains basically prevented any expansion to the east and it was the natural limit of Chile from the foundation of our capital on February 12, 1541 until today. Now, answering your second question. Why is there a country between southern Peru to the Strait of Magellan? the explanation is not simple but it can be simplified in one word: Gold. When the Spanish under the command of Francisco Pizarro (the Spanish conqueror who overthrew Atahaulpa), took control of the Inca territory, rumors began to circulate about a strange and inhospitable land on the southern limits of the Inca empire, a land in which the Gold was abundant, gold was one of the main reasons for the Spanish to conquer territories in the new world and their ambition for it knew no limit. in this way, one of Pizarro's companions, named Diego de Alamagro decided to make an expedition to this strange land, because the profits that he received for the conquest of Peru were very small compared to those of Pizarro, Almagro began his expedition in 1535, this was a complete failure. the resistance they found from the remnants of the Inca empire was fierce, Almagro also decided to cross the mountain range where temperatures reach degrees below zero, his men died in battle or from exhaustion and most terrible, nothing of Gold was found. after the failure of this Expedition, the lands to the south of the new Viceroyalty of Peru were considered cursed, but another young and ambitious Hidalgo, who wanted to leave his name written in the history of the conquest of America called Pedro De Valdivia decided to launch a second expedition Pizarro granted him permission and so Valdivia, on January 20, 1540, left Cuzco in the direction of the territory that was now known as Chile, and on February 12, 1541, Valdivia founded the city of "Santiago de la Nueva Extremadura" Today called Santiago de Chile our capital, and later he was named by the comrades of his host as Governor and the Emperor Carlos V of Habsburg recognized them as such, he is remembered as the founder of Chile and his equestrian statue was located in the main square of the capital .

But when the independence of Chile was declared on February 12, 1818 part of South America found itself with the borders that the Spanish empire handed over to the colonial administration, these borders were inherited by the new American states under the right of '' uti possidetis iuris '' and they changed throughout the 19th and 20th centuries. at that time Chile received the name of the "General Captaincy of Chile" and was part of the Viceroyalty of Peru. And the territories east of the Andes mountain range were under the administration of the Viceroyalty del Rio de la Plata founded in 1776. The General Captaincy of Chile at one point in its history administered territories east of the Andes, specifically the regions of Cuyo and Mendoza, but these were ceded to the Viceroyalty del Rio de la Plata the same year of its foundation in 1776. Now, the borders of Chile under Spanish rule at the time prior to the first government Junta (which started the independence period) ran from the city of Copiapo to the Bio-Bio river, these borders changed in the 19th century after the War of the Pacific (1879-1883) against Peru and Bolivia, of which Chile annexed part of its territories, and after the conquest of Araucania in 1888 where the Chilean state incorporated the lands of the Mapuche people. On the other hand, the Chilean state took possession of the Strait of Magellan on September 21, 1843 with the foundation of Fort Bulnes, the reason for this was to prevent other nations from taking over it due to its strategic potion. I hope I have helped you, I apologize if there is a spelling error since I use Google translator to write my answer.