From its inception in 1917, Saint Kilian Parish found its inspiration in the previous centuries of Catholic life and tradition. While rooted in that heritage, this parish has always sought to meet the contemporary needs of its members.

In 1917, at the request of the Catholic people in the Mars area, a mission church was established. The first Mass was celebrated by Fr. Timothy O'Shea on March 18, 1917, in Robertson's Hall. Fifty-two adults and thirty-three children attended. The area was first served by the Confraternity of Christian Doctrine under the direction of Fr. Dan Lawless, assisted by Fr. Victor Majka and Fr. Edward Heinrich. Fr. Weisenberger was followed by Fathers, A.C. Angel, J.B. Keating, G.T. Sheer, Charles Thomas, Fred Seibel, William Schaughnessy, Regis M. Hannon, Charles Schafer, Thomas Harvey, John W. Rebel and presently, Fr. Charles S. Bober.

In the spring of 1920 the congregation purchased an abandoned Free Methodist Church.  The building was renovated and repaired and was dedicated on December 5, 1920. This same building was remodeled, repaired many times, enlarged and served as St. Kilian Church until recently. The parish remained served by the Confraternity of Christian Doctrine until August of 1924 when the first resident pastor arrived in the parish, Rev. A. J. Weisenberger. At that time the parish was comprised of Mars, Bakerstown, Gibsonia, Cooperstown, Callery and Bairdford areas.

On July 4, 1934, fire struck the church.  Quick work by the local fire department saved the building, although it was heavily damaged.  While repair work was done on the church, Masses were held at Mars High School.  The Mars church hall was started by Father Seibel and completed in 1949 under Father Schaughnessy. The Mars rectory was built during Fr. Hannon's years at St. Kilian. Following Vatican Council II, many physical changes within the church became apparent, yet some memories were preserved in unique and meaningful ways. For example, when the altar rail was removed, it was converted into many tiny crosses and distributed to the parishioners as momentos. The CCD program was established in 1917 with an enrollment of 31 children. St. Kilian's first CCD teachers were Mrs. Margaret Morrison, Mrs. Rosina Weisenberg, and Miss Mary Killian. The CCD buildings were built in the 1970's and one was dedicated to Fr. Schafer.

From 1953 to 1973, the number of parishioners grew from 478 to 1,450 (more than 300%). The largest growth was experienced between 1983 to 2003 when the number of members grew from 1,650 to 7,016 or 425%. The same growth was reflected in the children attending CCD (K-8). From 1953 to present, the CCD attendance grew 1,000% from 81 to 900 children.As the parish grew, many options were considered. In 1962, Saint Kilian’s pastor, Father Charles Schafer, petitioned the Diocese for permission to build a new parish center (including a new church) on thirty-three acres some outside of the Borough of Mars. That initiative was not received favorably by Diocesan officials at that time but it demonstrated the continuing desire of this parish to consider the needs of the parish and what could be done to meet them. Today, we find ourselves part of that tradition.

In June, 2001, the boundaries of Saint Kilian Parish in Mars, PA, and Saint Ferdinand Parish in Cranberry, PA, were realigned. The result of this was a significant change and dramatic growth for Saint Kilian Parish. On July 2, 2001, Bishop Wuerl appointed Father Charles Bober as Pastor of Saint Kilian with the specific responsibility of preparing the people for this change and initiating the Second Century Campaign to raise funds for a much needed building project.

During the planning sessions for the new building project, it became evident that the influx of parishioners created a need for additional meeting space and CCD classrooms. With one-third of the parishioners being 17 years old and younger, the idea of also using the new space for a Catholic grade school was introduced. A survey to assess interest in a school was completed in the Fall of 2002, resulting in an overwhelming positive response.  The plans for the new school were initiated and construction began on the Franklin Road/Route 228 site in April, 2007. In Septemeber, 2008, Saint Kilian Parish School became the first, brand new Catholic grade school built in the Diocese of Pittsburgh in almost 40 years.