The people of Legnano obtained permission from Duke of Milan, Ludovico Sforza, to demolish its remains and to build a new church on the same site.

And this building would have been built to perfection in a much shorter time, had it not been for the calamity of war that this country suffered, in particular the land of Legnano, given that, falling in the street of Varese in the year 1511 on 10 December, with one side bleached and the rest sacked; it confirms the work of Alessandro Lampugnano, and conforms to what Guicciardino says in his story in the book X.

The second was that funding for the church had ceased; the primary donors, the local nobility, were made destitute after the French drove the Sforzas from the Duchy of Milan in 1499 and subsequent fighting.

[23] The work on the entrances was done by Francesco Maria Richini, a religious architect and the future designer of the Church of Madonnina dei Ronchi [it], also in Legnano.

[24][25] He also modified the basilica's exterior by adding Baroque elements like pilasters, pediments, and lintels to the new entrances, windows, and roof lantern.

[27] It was decided to open the central door because the two side entrances did not allow the visitor entering the basilica to be directly in front of the main altar.

[29] The design by Donato Bramante is confirmed by the papal bull of March 19, 1950 issued by Pope Pius XII which conferred the dignity of a Roman minor basilica on the church of Legnano:[30][25] [...] This temple, which dates back to the early 11th century, has been modified several times and finally rebuilt by the brilliant architect Donato Bramante, and constitutes a conspicuous ornament and decoration of the city.

[...] We raise to the dignity and honor of Basilica Minor the church consecrated to God in the name of St. Magnus, in the city of Legnano, located in the territory of the Archdiocese of Milan, with the addition of all liturgical privileges, that for this reason they compete.

[d]A hypothesis that explains the entitlement of the basilica to Magnus of Milan is linked to some events that took place a few decades after the Fall of the Western Roman Empire.

[31] In 523 the Byzantine emperor Justin I promulgated an edict against the Arians: in response, the king of the Ostrogoths Theoderic the Great, who was of the Aryan faith, began to persecute Catholics, killing and imprisoning important religious figures as well.

On the death of Theodoric, on the throne of the Ostrogoths, sat the most tolerant Athalaric: thanks to the new king, and to the intercession of Magno of Milan, the Milanese archbishop who was later proclaimed a saint, many prisoners were released.

[30] Faced with the displacement of the provost, the Parabiaghsis appealed to the pope, but without success, given the endorsement of the archiepiscopal decree by the Roman Curia, which occurred in 1586.

[30] On March 19, 1950, with a papal bull, Pope Pius XII raised the provost church of San Magno to a Roman minor basilica, from which the modern name descended.

It no longer follows the typical elongated rectangular shape towards the altar of medieval churches, but has a central octagonal plan that allows a perspective view in all directions.

[33] The Bramantesque churches do not have a main façade around which secondary volumes rotate, but they have a series of symmetries and perspective spaces that have about the same importance and form the whole of the entire structure.

[35] As already mentioned, the remains of the old one were transformed into a chapel, which is still visible behind the bell tower of the Basilica of San Magno on the south side of the building, near a covered passage.

[24] To this was also added the desire to create high-quality plastering works that should have been up to the recognized architectural and artistic value of the basilica of Legnano: this indecision on the type of decoration to be applied led to the expansion of the times of their execution.

[40] The choirs stalls, which are located inside the main chapel, were built in the 17th century in walnut wood by the Coiro brothers, or by the same carvers who carved the aforementioned small temple with a tabernacle in the sacristy.

[40][42] With the changes that took place in the first part of the 20th century, the ancient stalls of the choir of the basilica lost that austerity that was typical of the Renaissance period.

The organ of the basilica of San Magno, which is older than the one preserved in the Duomo of Milan, is perhaps the only pipe instrument manufactured by the Antegnati family that has come down to us practically intact.

Accompanied by the wise internal natural lighting originating from the side openings of the vault, which allow a calibrated luminosity at any time of day, the overall effect is of absolute importance,[39] so much so that even the art historian Eugène Müntz, who defined this decoration "the most beautiful grotesque in Lombardy".

[6] The painting is then completed with the representation of centaurs, dolphins, eagles, satyrs, sea horses, harpies, winged putti and dragons, whose dominant colors are white and gray in chiaroscuro.

[14] Just below the dome there is an octagonal tholobate which is frescoed with a softer shade than that of the vault: this is the opposite of what is generally done in the decorations of contemporary churches in the basilica, which are instead characterized by stronger colors in the lower parts and more tenuous in the upper architectural sections.

[46] The tholobate is characterized by the presence of twenty-four niches which are internally painted with a gray shade and with a rather dark blue color, which brings out the penumbra originating from the recesses: on the pillars of the drum are represented candelabras, which take up the decoration of the vault.

[46] In 1923 Gersam Turri painted in the spandrels, in the spaces between the major arches and in the capitals, twelve roundels, one in each architectural element, containing the faces as many biblical prophets (from left and right, starting from the arch located at the chapel of the Blessed Sacrament and of the outward, Joel, Daniel, Jonah, Obadiah, Amos, Haggai, Habakkuk, Zephaniah, Ezekiel, Micah, Zechariah, and Malachi), which were added to the four prophets previously painted: Jeremiah and Isaiah, which are above the major chapel and which were presumably made by Bernardino Lanino; Solomon and David, painted by the Lampugnani brothers above the arch of the chapel of the Holy Crucifix.

[3] The vault and walls of the main chapel were painted by Bernardino Lanino presumably between 1562 and 1564, at the height of his artistic maturity,[4] thanks to the economic contribution of the Lampugnani family.

[3] The lapel of the fresco that gives towards the center of the church is instead painted with candelabra of fruit and vegetables, while on the space between the triumphal arch and the pylons of the building there are two roundels that are supported by angels having the face of two prophets.

[51] The chapel contains a precious deposed wooden Christ, a crucifix and two papier-mâché statues depicting Our Lady of Sorrows and Mary Magdalene.

[51] The chapel located on the opposite side, which is called dell'Assumption o dell'Immacolate, houses the aforementioned altarpiece by Giampietrino from 1490 and an 18th-century wooden statue of the Immaculate.

[51] The chapel of the Andito, which is opposite, was not decorated by almost any painting to give an idea of how unadorned the basilica was before the realization of the pictorial works of the early 20th century.