The process of the Mexican independence was an event that ended the rule of the Viceroyalty of New Spain. Before the Napoleonic invasion of Spain in 1808, a Constituent Congress was convened in Cádiz, in September 1810. The result would be the Cádiz Constitution, signed in 1812 as a project to create the Spanish Nation. 

But while the sessions of the ‘Cortes de Cádiz’ were taking place, parallel uprisings had begun in America, activating a process of eventual separation of the viceroyalties from the Monarchy. This is the founding historic moment of Congress as a leading political figure for nations to be.