Which 1991 treaty established the South American trade bloc Mercosur?

The Treaty of Asunción established the South American trade bloc Mercosur in 1991.

Argentina, Brazil, Paraguay and Uruguay signed the treaty on 26 March 1991 in Asunción, Paraguay. Its central aim was to create a common market through the freer movement of goods, services and factors of production, along with a common external tariff and coordinated trade policy.

Mercosur is often described as a customs union, although its integration has not always been fully complete in practice. The bloc’s name comes from the Spanish Mercado Común del Sur, meaning Southern Common Market; in Portuguese it is called Mercosul.

The Treaty of Asunción supplied the founding framework, while the 1994 Protocol of Ouro Preto gave Mercosur its institutional structure. Venezuela later joined as a full member, but its membership has been suspended.