Since 22 September 2010, the Regiment's headquarters building has been a National Historical Monument following a declaration by the Argentine government on the occasion of the country's bicentennial year.

The regiment was formed as the Legión Patricia ("Patricians' Legion) from inhabitants of Buenos Aires in 1806 to fight against the British invasions of the River Plate.

Among some of its first members, it included a woman, the Alférez (approximately, second lieutenant) Manuela Pedraza, one of the heroes of the Defense of Buenos Aires in 1806.

Prior to the arrival of British troops, Viceroy Santiago de Liniers decided that volunteers are drawn from the population of Buenos Aires muster at the Fort on 15 September 1806.

Manuel Belgrano was elected Sergeant Major (later replaced by Juan José Viamonte) and among other officers commissioned were Feliciano Chiclana, Vicente López y Planes, and Eustace Perdriel Gregorio Díaz Vélez.

St. Martin of Tours became the patron of the unit and on 9 November the regimental colors were consecrated with full ceremonial at the Cathedral of Buenos Aires along with that of the Arribeños Corps.

The unit was then called the Buenos Aires Patrician Volunteer Urban Legion, with the status of a full Tercio or Colonial Regiment of Militia.

Regimental command Battalion composition In all: 69 Officers, 70 Sergeants, 20 Drummers, 179 Corporals, and 1,059 enlisted soldiers, for a total of 1,395 Patrician Legionnaires.

On 7 June 1807, during the battle of San Pedro in the Banda Oriental, the Spanish forces from Buenos Aires led by Francisco Javier Elio, including several companies of the Patricians Legion, were preparing to storm Colonia del Sacramento.

On January 1, 1809, the Cabildo of Buenos Aires, with support from the Spanish military units, tried to replace the viceroy Liniers with a Government Junta headed by Martin de Álzaga and create the "American Spain", before the occupation of Europe by the advancing Napoleonic armies.

Led by captain Diego Basavilbaso, two companies of the Patricians Corps joined the pacification forces of Vicente Nieto and Colonel Jose de Cordoba in Upper Peru that October, ending the revolutions on October 31 that year with Chuquisaca (today's Sucre in Bolivia) reoccupied by the royalist forces.

The May Revolution's main protagonists, Saavedra and the Patricians Corps would be successful during the days leading up to May 25, 1810, open cabildo of Buenos Aires, which resulted to the Viceroy's forced resignation and the birth of the Primera Junta.

Monday, May 14-Thursday, May 17 Upon hearing the news that by January, the Junta of Seville had fallen, Saavedra decided to let everyone take advantage of Napoleon's Peninsular Campaign to act against the Viceroyal government.

He and Juan Jose Castelli suggested having an open cabildo for this purpose, as against Martin Rodriguez's plan of revolutionary action against the Viceroy.

Monday, May 21 A riot led by the Legion Infernal (Infernal Legion) which demanded an Open Cabildo meeting and was interrupting the work of the Cabildo was quickly stopped by Col. Saavedra and he then called on the crowds gathered at the Plaza de la Victoria (today's Plaza de Mayo) to leave at once.

Wednesday, May 23 Two days of sessions by the Open Cabildo finally resulted in the vote and resolution formally calling the Viceroy to conclude his duties.

The Corps stood on alert all day to avoid riots and mass actions and to ensure a peaceful outcome of the session.

Thursday, May 24 The cabildo, now with the session done, formally announced the formation of a Junta with now ex-Viceroy Cisneros as president and Saavedra and Castelli as two of the four members (The two were Criollos while Spaniards occupied the other two).

While this was happening the Patrician Corps was guarding the Cabildo and the surrounding streets, on orders from Eustoquio Diaz Velez, together with soldiers from the other militia battalions.

Saavedra then spoke to everyone on what happened, and left the Cabildo on his way amid cannon salutes and bells, happy on his now concurrent posts as Patrician Corps Commander and as the new Junta President as well.

The order of June 8, 1810 (also by the First Junta) formally permitted racial integration into the new force of the mulattooes (blacks, pardos and natives) of the Castas Militia Battalion.

(repeat verse 1, then instrumental trio) The loud bugles vibrate, with brave war notes Reaching the confines of the hills, plains and mountains And if one day the voice of the Fatherland calls us to battle, Let us remember then those illustrious men That in Curupaytí, Salta and Tucumán, captured the colours like in Homer's days.