As God appointed Joseph, son of the Patriarch Jacob, over all the land of Egypt to store up corn for the people, so, when the fullness of time was come, and He was about to send to earth His only-begotten Son, the Savior of the world, He chose another Joseph, of whom the first had been the type, and He made him Lord and Ruler of His household and possessions, the Guardian of His greatest treasures. And Joseph espoused the Immaculate Virgin Mary, of whom was born by the Holy Ghost, Jesus Christ our Lord, who deigned to be reputed before men as the Son of Joseph and was subject to him.
And Him whom so many kings and prophets desired to see, Joseph not only saw, but abode with, and embraced with paternal affection, and kissed, yea, and most sedulously nourished, even Him whom the faithful should receive as the Bread come down from Heaven, that they might obtain eternal life.
On account of this sublime dignity which God conferred on His most faithful servant, the Church has always most highly honoured and lauded the Most Blessed Joseph next after his spouse, the Virgin Mother of God, and has implored his intercession in all her great necessities. And now that in this most sorrowful time the Church herself is beset by enemies on every side and oppressed by heavy calamities, so that impious men imagine that the gates of Hell are at length prevailing against her, the venerable prelates of the whole Catholic world have presented to the Sovereign Pontiff their own petitions and those of the faithful confided to their care, praying that he would vouchsafe to constitute St. Joseph Patron of the Catholic Church.
Moreover, when at the Sacred Ecumenical Council of the Vatican they renewed still more fervently this their petition and prayer, His Holiness, Pope Pius IX, moved thereto by recent deplorable events, was pleased to comply with the desires of the prelates, and to commit to the most powerful patronage of the Holy Patriarch Joseph both himself and all the faithful and solemnly declared him Patron of the Catholic Church, and commanded his festival, occurring on the 19th of March, to be celebrated as a double of the first class, but without an octave on the account of Lent.
Further, he ordained that on this day, sacred to the Immaculate Virgin Mother of God and Spouse of the Most Chaste Joseph, a declaration to that effect should by this present Decree of The Sacred Congregation of Rites be published.
Pius IX, Decree Quemadmodum Deus, December 8, 1870
Why Is St. Joseph the Patron of the Universal Church?
The special motives for which St. Joseph has been proclaimed Patron of the Church, and from which the Church looks for singular benefit from his patronage and protection, are that Joseph was the spouse of Mary and that he was reputed the Father of Jesus Christ.
As Joseph has been united to the Blessed Virgin by the ties of marriage, it may not be doubted that he approached nearer than any to the eminent dignity by which the Mother of God surpasses so nobly all created natures.
And Joseph shines among all mankind by the most august dignity, since by divine will, he was the guardian of the Son of God and reputed as His father among men. Joseph became the guardian, the administrator, and the legal defender of the divine house whose chief he was.
Now the divine house which Joseph ruled with the authority of a father contained within its limits the scarce-born Church.
And for such reasons the Blessed Patriarch looks upon the multitude of Christians who make up the Church as confided specially to his trust—this limitless family spread over the earth, over which, because he is the spouse of Mary and the father of Jesus Christ he holds, as it were, a paternal authority.
Leo XIII, Encyclical Quamquam Pluries, August 15, 1889