The Patagonian Republic of the Southern Seas is a seafaring nation born out of the ashes of the former Castilian colonies of Chile and Patagonia. Its history as a sovereign nation is fairly new, the Republic of Patagonia was formed in 1812 when revolutionaries took control of Patagonian terrory after several local uprisings in the recent years had weakened Castille's grip on the region. A new capital city, Magallanes, was founded at the southern end of the continent, where the Pacific and the Atlantic oceans meet, after pushing back the shattered Castilian colonial forces into the Chilean Andes. Over the next few years (an unspecified amount of) people from Castilian controlled Chile migrated to Patagonia to find a new life in freedom, and with the help of new information and manpower the Republican forces were able to liberate Chile in 1818. Many of those who migrated from Chile chose to stay in Patagonia even after the liberation of Chile, mainly living in the capital Magallanes (thus giving the region a slightly higher population than it has in the real world.)
After the liberation of Chile the Republic of Patagonia gained control of a large portion of the Castilian Pacific Navy, and when several island kingdoms in the Pacific were threatened by European colonists the new Patagonian Navy helped defend their lands. In 1827 the four kingdoms of Samoa, Tonga, Tahiti and Rapa Nui elected to join the Republic and were incorporated as the Patagonian Pacific Territory, forming the Patagonian Republic of the Southern Seas along with the states of Chile and Patagonia.