Three historical high points define this century.
Catholic American Church
The Catholic Church in America grew by leaps and bounds. Millions of immigrants from Germany, Ireland, Poland, Italy and the Slavic countries came to the United States. As the immigrant population increased more parishes were built and new dioceses came into existence. The American hierarchy held three plenary councils in Baltimore (1852, 1866 and 1884). The last council published the Baltimore Catechism and developed a parochial school system within each diocese.
Elizabeth Seton and John Neumann
Two saints that contributed to the growth and development of the Catholic Church in America were Elizabeth Ann Seton (1774-1821) and John Neumann (1811-1860).
After the death of her husband, Elizabeth Seton, a mother of five, left the Episcopalian Church and became Catholic. She dedicated her life to God by founding the Sisters of Charity who helped the poor by providing them with a Catholic education.
John Neumann, a Redemptorist missionary with zeal and fortitude, worked constantly to evangelize and teach the faithful. In 1852, St. John Neumann was elected Bishop of Philadelphia. To his credit he founded numerous parishes and parochial schools.
Pius IX, Vatican I and Leo XIII
During the reign of Pius IX (1846-1878) the Italian government along with anti-religious forces stripped the Pope and the Church of its property in an attempt to unify Italy. The papal states were reduced to what is known today as Vatican City. This prompted the Pope to declare himself the "prisoner of the Vatican". Pope Pius IX is known for calling the first Vatican Council into session, defining the doctrine of the Immaculate Conception and attacking liberalism with the document "The Syllabus of Errors".
With over 700 bishops in attendance, Vatican Council I (1869-1870) ended abruptly when war broke out between Prussia and France. The Council was never re-convened. One of the few documents that came out of the Council dealt with "papal infallibility". This document explained that in matters of faith and morals the Pope could not teach error due to a special grace given to him by the Holy Spirit.
Pius IX's successor was Pope Leo XIII (1878-1903). Pope Leo helped move the Church into the mainstream of modern society. His landmark encyclical "Rerum Novarum", published in 1891, was written as a response to the industrial revolution. The encyclical led the Church into the sphere of contemporary social action and helped further the Church's social teachings.
For further reading about St. Elizabeth Ann Seton, refer to the following:
Mother Seton and the Sisters of Charity by Alma Powers-Waters
Saint Elizabeth Ann Seton: Daughter of America (Encounter the Saints Series, 3) by Jeanne Marie Grunwell