Not a great deal is known about Juan Diego prior to his conversion...
A 'SACRED LITTLE HOUSE' FROM 1531 TO TODAY
With the future of Christianity on the American continent very much in doubt following Spain's conquest of Mexico, the Church was confronted by a native people who were wary of converting to the faith, a situation complicated by a hostile colonial government. It was under these circumstances that the newly-appointed bishop of Mexico wrote a letter to the king of Spain lamenting that the continent would probably be lost, short of a miracle. Obviously, that miracle occurred from December 9 - 12, 1531.
The appearance of Mary to the native Juan Diego on the hill in Tepeyac in 1531 had a decisive effect on evangelization. Its influence greatly overflows the boundaries of Mexico, spreading to the whole continent... [which] has recognized in the mestiza face of the Virgin of Tepeyac, in Blessed Mary of Guadalupe, and impressive example of perfectly enculturated evangelization.
-- John Paul II, Ecclesia in America
Following Our Mother's requests, Bishop Zumarraga, Juan Diego and the people in the area around Tepeyac hill immediately set about constructing the first shrine to Our Lady of Guadalupe, a small chapel that took only two weeks to complete. In the broader sense, it seems clear that Our Mother's request encompassed something infinitely greater than this humble little building, as one can easily see from the earliest fruits in the conversion of some 9,000,000 Aztecs to the Catholic faith.
Juan Diego continued to remain a part of this vibrant community throughout his lifetime, at the heart of Our Mother's mission to bring Eucharistic communion to all her children. To bring people to her Son, Jesus Christ.
BASILICA DE NUESTRA SENORA DE GUADALUPE
The Basilica of Guadalupe (Basilica de Nuestra Señora de Guadalupe) is the latest version of the shrine that began with the original chapel, a 'sacred little house' that Our Mother requested to be built during her apparitions to Juan Diego in 1531. Like the original chapel, it is a place where people can encounter Christ. It rests on the Sanctuary grounds on the exact site of the apparitions (Capilla del Cerrito) and near the Old Basilica that was solemnly dedicated in 1695 and finished in 1709. Juan Diego's tilma was housed in the Old Basilica until it was moved into the new church in 1974. Other chapels surround the area where at least 30 Masses are celebrated every day of the year.
The new Basilica of Guadalupe (Nueva Basilica) was built between 1974 and 1976 by the Mexican architect Pedro Ramirez Vasquez in a more modern style featuring a circular shape that allows for viewing of the miraculous tilma from any seat in the church.
The Basilica is considered the second most important sanctuary in the Catholic Church, just second to St. Peter's Basilica in Vatican City. There is enough seating for 10,000 people, however an additional 40,000 people can be seated in the atrium in order for them to participate in the Mass and other celebrations.