The purpose of this study was to narrate the continuous development of events in the Roman Catholic Church that led to the present Lafayette diocese in Indiana, 1677 to 1977. This diocese, created out of the Fort Wayne diocese on December 19, 1944, comprises the parishes in Indiana counties of Benton, Blackford, Boone, Carroll, Cass, Clinton, Delaware, Fountain, Fulton, Grant, Hamilton, Howard, Jasper, Jay, Madison, Miami, Montgomery, Newton, Pulaski, Randolph, Tippecanoe, Tipton, Warren, and White.Primary sources on this topic are here organized for the first time. Use of Canadian and American civil and ecclesiastical records identifies the Catholic missions around Fort Ouiatenon (near present Lafayette, Indiana) beginning 1677. From lists, charts, and maps derived primarily from parish registers at Sainte Anne de Detroit, St. Francis Xavier at Vincennes, official Catholie directories, the Lafayette and the amalgamation of the Potawatomi and Miami with the Canadians that became Indiana's first Americans.The American organization and growth of the Catholic Church in Indiana is told. Continuity with early settlers, namely, Yankee, Pennsylvania Dutch, and European Germans; analyses of Indiantreaties transferring land into annuities and business investments, and present involvement and statistics of church membership is described.This history's first part is in two sections. The first section covers 1677 to 1818, concentrating on French-British settlement among the Potawatomi and Miami under the Quebec diocese and the Canadian transition to American organization around Fort Ouiatenon. The second section from 1818 to 1858 narrates the early Church organization of Indiana under the Bardstown and Vincennes dioceses.The next part, from 1858 to 1908, is the narration of creation and growth of Fort Wayne diocese's parishes in the districts of northern Indiana that became the present Lafayette diocese. Personalities, rise of parochial schools and religious congregations are emphasized. The latter occurred in the episcopacies of Bishops John H. Luers, 1858-1871, Joseph G. Dwenger, 1872-1893, and Joseph J. Rademacher, 1893-1900.The fourth part of the study concerns the period from 1908 to 1977 in two sections. The first section from 1908 to 1944 shows Indiana's transition from agrarian to industrial economy and accompanying development of the Catholic Church from original missions of the Wabash River Valley. The effects of industrialization transforming farmers to factory workers and the newer immigration to northern Indiana's parishes are told in the administrations of Fort Wayne's Bishops Herman J. Alerding, 1900-1924, and John F. Noll, 1924-1957.The final section of this study completes the second section of part four of the dissertation. It shows how the early Catholic settlers of Indiana have survived and continue in today's organization of parishes. From 1944 to 1977 the actual episcopacy of Lafayette diocese's first three bishops is told; this period covers the work of Bishops John G. Bennett, 1945-1957; John J. Carberry, 1957-1965; and the first ten years of the incumbant Raymond J. Gallagher, 1.965-1975. Contemporary progress is also described.This history concludes that the American tradition to which the Canadian Catholics at Vincennes pledged the Catholic Church in Indiana has deep roots. The conclusion calls attention to the renewed recognition of Indiana's original settlers through the 1966 Roll of the Miami Nation stemming from the 1895 government roll based on this whole history. For three hundred years Catholicism in Indiana has developed from its oldest settlement around Fort Ouiatenon in 1717 until 1977 shows signs of continued vitality. The study concludes on a note' of continuity with the Roman Catholic Church as it has entered the American tradition as Indiana's oldest organized religion.