With the blessing of its final mosaic, America's Basilica – The National Shrine of the Immaculate Conception in Washington, D.C. – is finally complete after nearly a century of construction and adornment.

"This magnificent tribute in stone, glass, marble mosaic to Mary, Mother of Jesus, Mother of God and our Mother, invites all of us to recognize not only the special role of Mary in our life but the unique glory that is hers in her Immaculate Conception," said Cardinal Donald Wuerl of Washington in his Dec. 8 homily before the dedication of the basilica's new Trinity Dome mosaic.

Cardinal Wuerl blessed the dome with incense during Mass for the feast of the Immaculate Conception.  Cardinal Kevin Farrell, prefect of the Dicastery for the Laity, Family and Life attended the dedication as an envoy on behalf of Pope Francis and presented the cardinal and the rector of the Basilica, Msgr. Walter Rossi, with a letter of Apostolic Blessing from the Pope for the blessing.

The new dome and its mosaic, which depicts the Trinity, Mary, and nearly twenty saints and blessed who share a connection with either the Americas or the National Shrine itself, is the capstone which finishes 97 years of construction and decoration of the Basilica and its interior. Five cardinals, 23 bishops, nearly 90 priests, and over 4,000 people gathered to celebrate the event. Also present at the event were Cardinal Daniel DiNardo of Galveston-Houston, president of the U.S. Conference of Catholic Bishops, and U.S. Ambassador to the Vatican Callista Gingrich.

The construction of a National Shrine to Our Lady of the Immaculate Conception was announced in 1918 and construction began in 1920. "People were invited all over the country to contribute in whatever way they could," Cardinal Wuerl explained, and "some donated some pieces of old jewelry and others donated some precious stones."

After the completion of the Crypt Church in 1931, construction on the Upper Church was paused for the Great Depression and World War II, but resumed in 1945. The Church's structure was completed in 1959.

Since then, different side chapels depicting a variety of Marian apparitions, scenes from Mary's life, and other mosaics on the ceilings and walls have been completed. In addition, St. John Paul II dedicated the church as a basilica in 1979, and both Benedict XVI and Pope Francis have visited the shrine during their pontificates.

During his September 2015 visit to the shrine for canonization of Junipero Serra, Pope Francis blessed the first section of the Trinity Dome mosaic. The largest dome in the entire shrine, the mosaic contains more than 14 million pieces of handmade Venetian Glass. The artwork for the dome was designed by studios in New Jersey and Pennsylvania, and then fabricated in Italy into smaller puzzle-like sections. After being shipped over to the United States, the mosaic was then installed section by section onto the "crown jewel" of the shrine.

During his homily, Wuerl recalled an early gathering of United States bishops which chose the Blessed Mother of the Immaculate Conception to be the patroness for the young nation. "She is the supreme model of what our faith should be," the cardinal said. "She was the vessel of the incarnation."

The cardinal pointed to the new dome's many pieces coming together as one piece of art, drawing upon its reflection of the unity within the universal Church as well the many different cultures that have come together in the United States.

"Just as there are chapels throughout this Basilica reflecting national heritages, ethnic backgrounds, all proclaiming in unison 'Hail Mary,' so, too, do we look across this great Church of God and see out of so many one great faith family," Wuerl reflected.

Following his homily, Farrell read a special blessing from Pope Francis. Through his envoy, the Pope expressed his wish that all who gaze on Mary "show forth special love for the Church of Christ and the Gospel, even in our own age, and may distinguish themselves by their spiritual constancy." Farrell also said that the Pope asks that the faithful consider " the great honor and great gift that we have received from God's mercy and God's bounty."

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In addition to completing construction of the shrine, the blessing of the Trinity Dome is the first of a series of preparations for the upcoming 100th anniversary celebrations for the foundation of the basilica. A full series of centennial celebrations will take place around 2020.