Congress of Tucumán in the context of San Miguel de Tucumán

The United Provinces of the Río de la Plata (Spanish: Provincias Unidas del Río de la Plata), earlier known as the United Provinces of South America (Spanish: Provincias Unidas de Sudamérica), was a name adopted in 1816 by the Congress of Tucumán for the region of South America that declared independence in 1816, with the Sovereign Congress taking place in 1813, during the Argentine War of Independence (1810–1818) that began with the May Revolution in May of 1810. It originally comprised rebellious territories of the former Spanish Viceroyalty of the Río de la Plata dependencies and had Buenos Aires as its capital.

The name Provincias del Río de la Plata (formally adopted during the Cortes of Cádiz to designate the Viceroyalty of the Río de la Plata) alludes to the Junta Provisional Gubernativa de las Provincias del Río de la Plata or Primera Junta. It is best known in Argentinean literature as Provincias Unidas del Río de la Plata ('United Provinces of the River Plate' i.e. 'river of silver'), this being the most common name (since 1811) in use for the country until the enactment of the 1826 Constitution. The Argentine National Anthem refers to the state as "the United Provinces of the South". The Constitution of Argentina recognises Provincias Unidas del Río de la Plata as one of the official names of the country, referred to as "Argentine Nation" (Nación Argentina) in modern legislation.

The Independence of the Argentine Republic (or La Independencia de Argentina in Spanish) was declared on July 9, 1816, by the Congress of Tucumán. In reality, the congressmen who were assembled in Tucumán declared the independence of the United Provinces of South America, which is one of the official names of the Argentine Republic. The Federal League Provinces, at war with the United Provinces, were not allowed into the Congress. At the same time, several provinces from the Upper Peru that would later become part of present-day Bolivia, were represented at the Congress.

The Argentine War of Independence (Spanish: Guerra de Independencia Argentina) was a secessionist civil war (until 1816) fought from 1810 to 1818 by Argentine patriotic forces under Manuel Belgrano, Juan José Castelli, Martin Miguel de Guemes and José de San Martín against royalist forces loyal to the Spanish crown. On July 9, 1816, an assembly met in San Miguel de Tucumán, declaring independence with provisions for a national constitution.

The Federal League (Spanish: Liga Federal), also known as the League of the Free Peoples (Liga de los Pueblos Libres), was a short lived confederation of provinces located in South America. From 1815 to 1820 it tried to establish a confederal organization for the State that was emerging from the May Revolution in the war of independence against the Spanish Empire in part of what is now Uruguay, Argentina and Brazil.

Founded and led by José Gervasio Artigas, it proclaimed independence from the Spanish Crown in 1815 and sent provincial delegates to the Congress of Tucumán with instructions regarding the nonnegotiable objective of declaring full independence for the United Provinces of the Río de la Plata and establishing a confederation of provinces, all of them on equal footing and the government of each being directly accountable to its peoples by direct democratic means of government. The delegates from these provinces were rejected on formalities from the Congress that declared the independence of the United Provinces of South America on July 9, 1816.

The Army of the Andes (Spanish: Ejército de los Andes) was a military force created by the United Provinces of the Río de la Plata (Argentina) and assembled by General José de San Martín as part of his campaign to liberate Chile from the Spanish Empire. In 1817, it crossed the Andes Mountains from the Argentine province of Cuyo (with its staging point being the present-day province of Mendoza, Argentina) and succeeded in its objective by driving the Spanish out of Chile.

The exact number of soldiers in the army varies among sources, with estimates ranging from as low as 3,500 to as high as 6,000 men. The army was composed of Argentines and Chileans, and included approximately 1,200 auxiliaries who assisted with provisioning and supply, along with a complement of artillery. The Congress of Tucumán endorsed San Martín's proposal to form an army to fight the royalists in Chile, and between August 1814 and February 1817, San Martín trained his troops in preparation for their mission. Although the army was less experienced, San Martín aimed to lead a properly disciplined and equipped force into battle, not a mere "motley crew."