Estanislao López (26 November 1786 – 15 June 1838) was a caudillo and governor of the province of Santa Fe, Argentina, between 1818 and 1838, one of the foremost proponents of provincial federalism, and an associate of Juan Manuel de Rosas during the Argentine Civil War.After this, in 1818, López assumed the government of Santa Fe, deposing governor Mariano Vera, separating the province from Buenos Aires control, and ruling by popular consensus for 20 years.López rejected a draft for a provincial constitution for Santa Fe (which accepted a centralized government from Buenos Aires), and wrote another one, where he incorporated the idea of popular election of the governor by direct vote, which was approved on 26 August 1819.[1] López allied with Artigas and then with Francisco Ramírez, caudillo of Entre Ríos, amassing large armies against Buenos Aires, at the time ruled by Supreme Director Juan Martín de Pueyrredón.General José de San Martín, Liberator and hero of the Independence Wars, wrote separate letters to López and Artigas urging them to cease hostilities and join the national cause.