Louis A. DeSimone was born on February 21, 1922 in Philadelphia, but reared in Bridgeport, Pennsylvania. He is a graduate of Bridgeport High School and Villanova University. During World War II, he was a Sergeant in the U. S. Army and served in Italy for two years with the Fifth Army Headquarters. Upon his return, he entered St. Charles Seminary, Overbrook, Pennsylvania, and was ordained a Priest on May 10, 1952.
As a priest, Father DeSimone taught at St. Thomas More High School in Philadelphia, served as assistant pastor at St. Donato Parish in Philadelphia and at SS. Cosmas and Damian Parish in Conshohocken, PA. In 1961 he was appointed to the Executive Committee of the Catholic Charities Appeal of the Archdiocese. In 1968 he was appointed as pastor of SS. Cosmas and Damian Parish. In 1971, Cardinal Krol named him Archdiocesan Director of Catholic Relief Services. In 1975, he was appointed chairman of the Heritage Group Committee for the 41st International Eucharistic Congress which took place in Philadelphia in August of 1976. That same year, Father DeSimone was named an honorary prelate with the title of Monsignor. Cardinal Krol chose him to be coordinator of the Italian Earthquake Relief Fund for Friuli which combined the efforts of the Archdiocese, the City of Philadelphia and the Order of the Sons of Italy in America. In recognition of his work, the Italian Government awarded him the "Commendatore al Merito della Repubblica Italiana."
In November of 1976, Monsignor DeSimone was appointed pastor of St. Monica Church, Philadelphia. In 1979 he was named a Diocesan Consultor and a member of the Council of Managers of the Archdiocesan Office for Development.
Monsignor DeSimone served for several years as a member of the Board of Directors of Pennsylvania Hospital and of Methodist Hospital. He was also a Vice-President of the United Way of Southeastern Pennsylvania.
Because of the earthquake which devastated Southern Italy on November 23, 1980, Monsignor DeSimone became immediately involved in the activities of the Catholic Relief Services. Cardinal Krol wished him to visit the disaster area to assess first-hand the precise needs of those afflicted. He was accompanied to Italy by Larry Kane, Anchorman for Channel 3 in Philadelphia, who wanted to bring the story to the people of the Delaware Valley.
On August 12, 1981 Monsignor DeSimone was ordained a bishop and named Vicar General of the Archdiocese. In 1982 he was named chairman of the Catholic Charities Appeal.
Bishop DeSimone has a brother, Father Russell J. DeSimone, O.S.A. who is Professor of Patristic Theology at the Lateran University in Rome. Another brother, Monsignor Salvatore R. DeSimone, died on August 2, 1989 while pastor of St. Thomas Church in Brigatine, NJ.