Probably, originally it must have consisted only of a chapel made of light materials, such as straw and mud; and at least since 1544, there is news that masses were no longer celebrated outdoors, so a suitable building had to be created to carry out Catholic practices.
However, later, its main access would be facing the square, in the so-called "Puerta del Perdón"; especially after a controversy that occurred around the year 1600, where it was argued that the north door should be closed due to the indecency of the houses that were in front of it (because they were neighbors and not part of the cult).
On May 13, 1647, an earthquake affected the central area of the Captaincy General of Chile, destroying almost the entire city of Santiago along with the cathedral.
The plans for this new cathedral were the work of Pedro Vogl and Juan Hagen, two members of the Society of Jesus, of Bavarian origin, who sent their project to Spain for royal approval in 1753.
Bishop González acquired the properties next to the cathedral, at the corner of the current Catedral and Bandera streets, which belonged to the Pineda Bascuñán family; and decided to place the feet (the Altar) of the new building in Bandera and the front in the square, with a length of 100 meters, changing the direction that had originally been arranged by Valdivia in the 16th century.
On the night of December 22, 1769, a fire broke out that destroyed the entire old cathedral, probably because the oil from the lamp that illuminated the Blessed Sacrament had spilled on some combustible object.
Only five years later, the prelate entrusted the Italian architect Joaquín Toesca with the execution of the facades of the cathedral and the Church del Sagrario.
Toesca redid the plans, beginning by directing the works in the damaged sector, next to the square, and modifying part of the area already built, with which the temple was architecturally enriched.
Around 1830 the building was almost finished, and in 1840, Pope Gregory XVI turned it into a Metropolitan Cathedral, elevating the seat of Santiago to Archiepiscopal rank.
The order or decree of erection was later lost, so Pope Pius IX allowed a new one to be made, leaving September 29, 1873 as the definitive date.
In November 1849, the organ It arrived in Valparaíso by boat, and for its placement a choir had to be built over the main door of the cathedral, which in its first period was reinforced by fourteen English iron pillars arranged under it.
At the end of the 19th century, Archbishop Mariano Casanova ordered a series of modifications that transformed the Cathedral into the building it currently exists.
The second option, and it was definitely left, was to leave it under the arch, which enormously increased the size of the choir but significantly restricted the sound capacity of the organ.
In the central nave, the old main altar stands out at its bottom, crowned by a marble ciborium that preserves the crucifix inside, crowned by an eagle and guarded by angels, which was built in Munich in 1912, where masses were celebrated until that, between the 1960s and 1970s, in the archbishopric of Cardinal Raúl Silva Henríquez, a mobile wooden altar was made to celebrate Mass facing the town, but since it was not very decent for the surroundings, a front was placed in front of it silver 3 meters long.
On the other hand, in the choir that is located above the main door, there is the great pipe organ made in the Flight & Son house in London.
Formerly the crypt was a dark and battered place but, at the initiative of Cardinal Carlos Oviedo Cavada, a project was drawn up to build a new one under the main altar, more worthy of preserving the remains of the prelates.
Remodeled in 2005, it currently has a modern and sober appearance, headed by a colonial Christ in a crucifixion attitude and a small granite altar.
Next to the right door of the Plaza de Armas is the monument and marble amphora where the hearts of the Chilean officers killed in the Battle of La Concepción in 1882 are preserved.