The purpose of this article is to determine whether the Catholic religion has continued to modernize since Vatican II. To help analyze the modernization of Catholicism, this article will examine the immigration of Catholics to America in the 19th and 20th centuries. Throughout this article, I will reference the commentary of Dr. Julie Byrne, professor of American religious history at Duke University, to explain how Catholicism has assimilated into American culture. Next, this article suggests three challenges currently facing Catholics in the 21st century. Finally, this article will expand on the growth of “irreligious Catholics” and its potential dangers. Although Catholicism assimilated into American culture during the 19th and 20th centuries, research and the rise of "irreligious Catholics" in the 21st century suggest that Catholicism may not have continued to modernize. In Dr. Byrne's article, "Roman Catholics and Mainstream America in the Twentieth Century," she identifies two transitional periods in American history that reshaped Catholicism. Dr. Byrne's article focuses on the immigration of Catholics to America between 1840 and 1920. In Dr. Byrne's article, she analyzes the immigration of Catholics during these centuries and concludes that each wave of immigration has contributed to the modernization of Catholicism. Dr. Byrne deepens his analysis by examining the overarching challenges that Catholic immigrants faced as they transitioned to the New World. Dr. Byrne believes that the challenges Catholic immigrants faced in America during the 19th century were due to "demographic" confrontations. Dr. Byrne also believes that Catholic immigrants of the 20th century largely suffered... middle of paper... they consciously continue to apply the apostolic tradition. However, it may not be so easy for future generations not socialized into Catholicism to make effective moral decisions. Therefore, this article suggests that the future of ecumenism depends on whether or not the Catholic Church can continue to modernize. Works Cited by Byrne, Dr. Julie. "Roman Catholics and Immigration in Nineteenth-Century America, Nineteenth-Century, Divine America: Religion in American History, TeacherServe, National Humanities Center." National Center for the Humanities and Duke University, November 2000. Web. December 8, 2011. nkeyinfo/nromcath.htm>. Rausch, Thomas P. “Chapter 9: A Truly Catholic Church.” Towards a truly Catholic Church: an ecclesiology for the third millennium. Collegeville, MN: Liturgical, 2005. 167-81. Print.