What would South America be like if Louisiana hadn't been sold in 1803? Southern Eagle Uchronia.
Image: Southamerica in 1890 after Treaty of Portales.
It all begins in 1803, when Napoleon decides not to sell Louisiana to the United States, considering the territory too important to give up. Because of this decision, Britain is able to occupy New Orleans in 1809 after a military campaign, establishing a strong presence along the Mississippi River. The United States sees the British occupation of New Orleans as a direct threat to its expansion westward, leading to the Anglo-American War of 1812–1815. The war ends in a British victory, forcing the United States to recognize the Mississippi River as its western border. As a result, the United States never achieves Manifest Destiny, and its ability to pressure the rest of the Americas is greatly reduced. Without a dominant northern power expanding across the continent, South America is left with far more freedom to develop its own political and military balance.
In 1833, the War of the Farrapos breaks out between the Empire of Brazil and the rebels of Pará, Amazonia, and Rio Grande do Sul. What begins as a regional rebellion in southern Brazil quickly expands into a wider crisis, with northern separatist movements opening new fronts against the imperial government. After several decisive battles, Brazil is forced to surrender in 1839 and recognize the independence of Pará, Amazonia, and Rio Grande do Sul. Chile recognizes and assists Rio Grande during the conflict, seeing the weakening of Brazil as a strategic opportunity. This early support creates a close relationship between both states, and in 1840 their defensive alliance is formally established.
In 1836, the War of the Confederation begins between Peru-Bolivia and the alliance of Chile and Argentina. In our timeline, Blanco Encalada withdrew after the failure of the first expedition and signed the Treaty of Paucarpata. In this alternate timeline, however, he refuses to return empty-handed and instead captures the port of Cobija. After the war, Chile annexes Cobija in the peace settlement, giving the country an earlier and stronger position in the nitrate-rich north.
By 1843, Chile seeks to expand further into Patagonia and founds the city of Portales in Neuquén, named in honor of the deceased Chilean leader Diego Portales. This expansion is helped by the Treaty of Peace and Friendship with indigenous groups, in which Chile recognizes their autonomy in exchange for weapons, protection, and mutual cooperation. This allows Chile to expand rapidly along the Colorado River, founding several settlements and strengthening its presence in Patagonia.
In 1844, the Second War of the Farrapos breaks out. This time, new rebels from Goiás, Mato Grosso, and Rondônia rise against the weakened Empire of Brazil, supported by Rio Grande and Amazonia. Brazil, still damaged by the previous war, is unable to contain the rebellion. Rio Grande expands further north, Amazonia also gains new territories, and several new states become independent. The war ends with the further balkanization of Brazil and a republican coup that brings down the imperial system.
The Argentine Civil War also develops differently from our timeline. Instead of the unification process that occurred historically, the Federalists win in 1861 after the Battle of Cepeda. This creates a much weaker, more divided, and more separatist Argentina, unable to project power in the same way as in real history.
Between 1851 and 1860, Rio Grande do Sul begins a process of growing influence over Uruguay. By 1855, after the death of Rio Grandese ministers appointed in Uruguay, a civil war breaks out. The conflict ends with the victory of the pro-Rio Grande faction, turning Uruguay into a dependent state under Rio Grandese influence.
During the 1860s and 1870s, Chile experiences a nitrate boom. Because it had annexed Cobija earlier, Chile discovers and exploits nitrate resources sooner than in our timeline. The country produces nitrate on a much larger scale and benefits economically from its export. This creates a demographic boom, strengthens the Chilean state, and provides greater funding for military modernization.
By the late 1870s, Chile had become much stronger thanks to the nitrate boom in the north. The earlier annexation of Cobija had allowed Chile to discover, exploit, and export nitrate on a much larger scale, giving the country more money, better infrastructure, and a more modern military. This also made Chilean companies and workers increasingly important in the Atacama region, where nitrate had become one of the most valuable resources in South America.
The crisis began when Bolivia raised taxes on Chilean nitrate companies from 5% to 10%. Chile considered this a violation of previous agreements, while Bolivia saw it as a way to reassert control over its resources. When the Chilean companies refused to pay, the Bolivian government responded by expropriating Chilean-owned nitrate properties and attacking Chilean interests in Tocopilla. For Chile, this was the breaking point. Santiago ordered the navy north, and the conflict quickly escalated into the first phase of the Great South American War: the War of the Pacific.
At the start, the war was focused on control of the coast. Chile landed troops in Tocopilla in 1879 and began securing the desert ports, while Peru entered the war because of its secret alliance with Bolivia. Naval control became decisive. Battles such as Iquique, Punta Gruesa, and the capture of the Huáscar gave Chile dominance over the Pacific, allowing it to move troops, supplies, and artillery along the coast far more effectively than Peru or Bolivia could respond.
Once Chile controlled the sea, the war expanded inland. The Chilean army advanced through the desert and into the Andean interior, fighting for key positions such as Calama, Arica, Tacna, Oruro, Puno, and Juliaca. The campaign was not a simple coastal invasion; it became a long war of logistics, mountain routes, ports, railways, and desert supply lines. Bolivia was slowly pushed back from the coast and the highlands, while Peru lost control of much of its southern territory, Chile even attempted to land in Lima in 1881, but failed because it concentrated all its forces on the northern front.
Between 1882 and 1885, Chile experienced a paralysis on the northern front due to the high plateau and poor logistics, turning the conflict into a violent war of attrition. For this reason, Chile landed troops in Lima again at the end of 1882, although they were still unable to advance beyond occupying the coastal districts.
By 1884, Peru and Bolivia were severely weakened, but neither accepted Chilean terms. The Conference of Antofagasta failed, and the war continued into 1885. At that point, the conflict changed completely. Argentina, worried by Chile’s growing power and its expansion in Patagonia, issued an ultimatum over the southern border. Chile refused to back down, and Argentina entered the war. This marked the beginning of the second phase: the Great Southamerican War.
The Great Southamerican War transformed the conflict from a Pacific war into a full South American struggle. Chile was now joined by its allies, especially Rio Grande do Sul and Paraguay, while Argentina fought alongside the already weakened Peru and Bolivia. The war expanded across several fronts: Patagonia, the Río de la Plata, the Chaco, Bolivia, Peru, and the Argentine interior.
Argentina expected to contain Chile in Patagonia and pressure its allies, but the war quickly became harder than expected. Rio Grande do Sul opened a front in the Atlantic and along the Plata region, while Paraguay attacked from the north. Chile continued pushing through Bolivia and Peru while also fighting Argentina in the south. Instead of facing one enemy, Argentina was forced to divide its army across multiple fronts, weakening its ability to respond effectively.
As the war dragged on, the Argentine situation worsened. Allied naval pressure, blockades, internal instability, and the strain of feeding several fronts created a major logistical collapse. Buenos Aires tried to hold the war effort together, but the interior became increasingly unstable and exhausted. The conflict became less about single decisive battles and more about the collapse of Argentina’s ability to keep fighting.
By 1888, Bolivia was effectively defeated. By 1889, Peru was also forced out of the war and allies financed revolts in the Argentinians Provinces. Argentina was left isolated, surrounded, and exhausted. In 1890, the allied forces launched the final campaign against Buenos Aires. After the fall of the city, Mendoza, Salta, Tucuman,¿ and Cordoba declared independence, while Entre Rios was occuped by Rio Grande do Sul. Argentina could no longer continue the war, and the remaining governments were forced to negotiate.
The war officially ended with the Treaty of Portales in 1890. The treaty completely reorganized South America. Chile emerged as the dominant power of the Pacific, Rio Grande do Sul became the main power of the Atlantic south, Paraguay gained influence in the interior, and the defeated states were left weakened, occupied, divided, or politically controlled.
Chile emerged as the main winner of the treaty. It secured control over the nitrate-rich northern territories, strengthened its position in Patagonia, and became the dominant power on the Pacific coast. Bolivia lost its access to the sea and was left politically weakened, while Peru was placed under heavy Chilean influence and forced to accept major territorial and military restrictions.
Argentina suffered the harshest consequences. The country was divided, occupied, and politically reorganized after the collapse of Buenos Aires. Rio Grande do Sul expanded its influence over the Río de la Plata region, while Paraguay gained greater control and prestige in the interior. The treaty also imposed reparations, disarmament, and foreign oversight on the defeated powers.
For the victorious states, the Treaty of Portales created a new balance of power in South America. For the defeated countries, it became a symbol of humiliation and foreign domination. Although it ended the war, it also planted the seeds of future resentment, nationalism, and revenge movements that would later destabilize the continent again.
The treaty, for the defeated countries created deep resentment across the continent. In Argentina, Peru, and Bolivia, Portales became a symbol of humiliation, foreign domination, and national collapse. The defeated countries were left unstable, economically damaged, and politically divided, which allowed extremist and revanchist movements to grow in the following decades. Although the treaty ended the Great South American War, it did not bring real peace; it only froze the conflict and prepared the ground for future wars.
You can also visit the alternate history wiki at these links: Main Page , Great Southamerican War