Juan Manuel José Domingo Ortiz de Rosas, nicknamed "Restorer of the Laws", was an Argentine politician and army officer who ruled Buenos Aires Province and briefly the Argentine Confederation. Although born into a wealthy family, Rosas independently amassed a personal fortune, acquiring large tracts of land in the process. Rosas enlisted his workers in a private militia, as was common for rural proprietors, and took part in the disputes that led to numerous civil wars in his country. Victorious in warfare, personally influential, and with vast landholdings and a loyal private army, Rosas became a caudillo, as provincial warlords in the region were known. He eventually reached the rank of brigadier general, the highest in the Argentine Army, and became the undisputed leader of the Federalist Party.

Buenos Aires, officially the Buenos Aires Province, is the largest and most populous Argentine province. It takes its name from the city of Buenos Aires, the capital of the country, which used to be part of the province and the province's capital until it was federalized in 1880. Since then, in spite of bearing the same name, the province does not include Buenos Aires city, though it does include all other parts of the Greater Buenos Aires metropolitan area. The capital of the province is the city of La Plata, founded in 1882.