The word basilica is derived from the Greek word meaning "royal house." In the Catholic faith, a basilica is a church building that has been accorded special privilege by the pope. There are two kinds, the major and the minor.
There are only four major basilicas all of which are in Rome, Saint John Lateran, Saint Peter, Saint Paul Outside the Walls, and Saint Mary Major also known as Santa Maria Maggiore.
The title of major basilica was introduced in 1300 by Pope Boniface VIII when he elevated Saint Peter and Saint Paul Outside the Walls. Saint John Lateran was added in 1350 and Saint Mary Major in 1390.
More than 1,580 churches around the world are minor basilicas, including my own parish church, Carmel Mission Basilica.
On August 4, 358, Pope Liberius received a vision in a dream to build a church in honor of the Blessed Virgin Mary. He would find the area for this church marked by snowfall. The following morning on August 5, snow fell on Esquilline Hill. Tradition holds that Pope Liberius traced the outline for the church in the snow.
The present church of Saint Mary Major was built under Pope Sixtus III after the Council of Ephesus of 431 proclaimed Mary Theotokos, Mother of God.
Photo of the Basilica of Santa Maria Maggiore - Wikipedia