Friday, May 25
On the morning of May 25, in spite of bad weather, a crowd gathered in the Plaza de la Victoria, as did the militia led by Domingo French and Antonio Beruti. They demanded the recall of the Junta elected the previous day, the final resignation of Cisneros, and the appointment of a new junta that did not include him. Historian Bartolomé Mitre stated that French and Beruti distributed blue and white ribbons, similar to the modern cockade of Argentina, among those present. Later historians doubt it, but consider it possible that the revolutionaries used distinctive marks of some kind for identification. It was rumored that the Cabildo might reject Cisneros' resignation. Because of delays in issuing an official resolution, the crowd became agitated, clamoring that "the people want to know what is going on!".
The Cabildo met at 9 am and rejected Cisneros' resignation. They considered that the crowd had no legitimate right to influence something that the Cabildo had already decided and implemented. They considered that, as the Junta was in command, the demonstration should be suppressed by force, and made the members responsible for any changes to the resolution of the previous day. To enforce those orders, they summoned the chief commanders, but these did not obey. Many of them, including Saavedra, did not appear. Those that did stated that they could not support the government order, and that the commanders would be disobeyed if they ordered the troops to repress the demonstrators.
The crowd's agitation increased, and they overran the chapter house. Leiva and Lezica requested that someone who could act as spokesman for the people should join them inside the hall and explain the people's desires. Beruti, Chiclana, French and Grela were allowed to pass. Leiva attempted to discourage the rioter Pancho Planes, but he entered the hall as well. The Cabildo argued that Buenos Aires had no right to break the political system of the viceroyalty without discussing it with the other provinces; French and Chiclana replied that the call for a Congress had already been considered. The Cabildo called the commanders to deliberate with them. As had happened several times in the last few days, Romero explained that the soldiers would mutiny if forced to fight against the rioters on behalf of Cisneros. The Cabildo still refused to give up, until the noise of the demonstration was heard in the hall. They feared that the demonstrators could overrun the building and reach them. Martín Rodríguez pointed out that the only way to calm the demonstrators was to accept Cisneros' resignation. Leiva agreed, convinced the other members, and the people returned to the Plaza. Rodríguez headed to Azcuenaga's house to meet the other revolutionaries to plan the final stages of the revolution. The demonstration overran the Cabildo again, and reached the hall of deliberations. Beruti spoke on behalf of the people, and said that the new Junta should be elected by the people and not by the Cabildo. He said that, besides the nearly 400 people already gathered, the barracks were full of people who supported them, and he threatened that they would take control, by force if necessary. The Cabildo replied by requesting their demands in writing.
After a long interval, a document containing 411 signatures was delivered to the Cabildo. This paper proposed a new composition for the governing Junta, and a 500-man expedition to assist the provinces. The document—still preserved—listed most army commanders and many well-known residents, and contained many illegible signatures. French and Beruti signed the document, stating "for me and for six hundred more". However, there is no unanimous view among historians about the authorship of the document. Meanwhile, the weather improved and the sun broke through the clouds. The people in the plaza saw it as a favorable omen for the revolution. The Sun of May was created a few years later with reference to this event.
The Cabildo accepted the document and moved to the balcony to submit it directly to the people for ratification. But, because of the late hour and the weather, the number of people in the plaza had declined. Leiva ridiculed the claim of the remaining representatives to speak on behalf of the people. This wore the patience of the few who were still in the plaza in the rain. Beruti did not accept any further delays, and threatened to call people to arms. Facing the prospect of further violence, the popular request was read aloud and immediately ratified by those present.
The Primera Junta was finally established. It was composed by president Cornelio Saavedra, members Manuel Alberti, Miguel de Azcuénaga, Manuel Belgrano, Juan José Castelli, Domingo Matheu and Juan Larrea, and secretaries Juan José Paso and Mariano Moreno. The rules governing it were roughly the same as those issued the day before, with the additional provisions that the Cabildo would watch over the members of the Junta and that the Junta itself would appoint replacements in case of vacancies. Saavedra spoke to the crowd, and then moved on to the Fort, among salvos of artillery and the ringing of bells. Meanwhile, Cisneros dispatched a post rider to Córdoba, Argentina, to warn Santiago de Liniers about what had happened in Buenos Aires and to request military action against the Junta.