On Easter Sunday, 10 April 1887, Pope Leo XIII gave permission to James Cardinal Gibbons, the Archbishop of Baltimore, for the establishment of the Catholic University of America in the letter Quod in novissimo conventu.

Pope Leo was strongly supportive of the university, writing, “Go on therefore, Beloved Son, together with all Our other Venerable Brethren the Bishops of the United States, to carry to perfection with one mind what you have begun; and let not any one of you be deterred by any difficulty or labor, but let all take courage from the assured hope that they will receive an abundant return for their cares and solicitudes.” He wanted the university to provide the Church with “worthy ministers” for evangelization and the saving of souls and to provide the United States with “her best citizens”.

Ever since October 1866, at the Second Plenary Council of Baltimore, the US bishops had expressed to the Vatican their desire to establish a university. At the Third Plenary Council of Baltimore in 1884, Washington DC was selected as the site. On 7 March 1889, Pope Leo XIII issued the Apostolic Letter Magni nobis gaudii which approved the constitution and statutes, and granted the university the power to offer degrees. Classes officially began on 13 November 1889.

More on the history of the Catholic University of America
Quod in novissimo conventu in Latin can be found here
Magni nobis gaudi