Battle of Seival
1836 CE.
Shown on the map at -31.419°, -53.726°.
The Battle of Seival took place on 10 September 1836 between Ragamuffin rebels and forces loyal to the Empire of Brazil during the Ragamuffin War's early stages; the rebel victory in this battle led to the proclamation of the Riograndense Republic as a breakwaway state from the Empire of Brazil.
Text from the Wikipedia article Battle of Seival, licensed CC BY-SA 4.0.