The first inhabitants were the Guarani Indians whose main activities were agriculture, fishing and hunting. Founder Don Juan de Garay distributed lands of the so-called “Pago de la Costa” or “Monte Grande”, situated in The Santisima Trinidad city, the current space occupied by San Isidro.
A Basque Captain, Domingo de Acassuso bought land here and commissioned the building of a chapel and the creation of a chaplaincy under the protection of San Isidro Labrador, who was the saint patron of his family in Spain. There was nothing left of the original chapel built in 1707 but the grounds are today occupied by the cathedral.
With the passing of the years the area became popular with the Porteño aristocracy who started building their villas here surrounded by huge gardens and gave San Isidro the particular air it still has despite modern changes. San Isidro has at present over 300,000 inhabitants and is formed by the localities of Acassuso, Beccar, Boulogne, Martinez, San Isidro and Villa Adelina.