On June 24, 1945, in the presence of twenty-five people, ground was broken by Father William Pezold, the Pastor of Saint Joseph Parish in Cottleville. The cornerstone of what is now St. Joseph Chapel was placed on August 26, 1945, by Monsignor (later Bishop) Leo Steck, with the Most Reverend John J. Glennon, Archbishop of St. Louis, presiding. It was Archbishop Glennon who designated the new mission parish to be named "Immaculate Heart of Mary," the first parish in the Archdiocese with that title. The mission parish was comprised of about twenty families at that time. Several of the "charter members" and many of the children of these families are still members of the parish.

The blessing and dedication of the church took place on Sunday, December 9, 1945. The grotto, in honor of Our Lady of Fatima, was built by some of the men of the parish, and was dedicated on October 26, 1947, by Father Wenceslaus Svehla, Assistant Pastor of St. Joseph's Parish in Cottleville.

On April 5, 1956, the mission was raised to the status of a full parish, and a rectory was built for a resident priest. Father Pezold said Mass for the last time at Immaculate Heart of Mary on April 8, 1956. Father Arthur Bromschwig was appointed as administrator, while also serving at Duchesne High School in St. Charles. The rectory was blessed on October 7, 1956. Father Bromschwig later supervised the construction of the new St. Dominic High School in O'Fallon, while still serving as Administrator of this parish.

Many of the parishioners desired parochial education for their children, so arrangements were made with the parish schools at Immaculate Conception in Dardenne and St. Joseph's in Cottleville to accept children from our parish. Catechetical instruction was provided for the children attending public grade and high schools. In order to finance the purchase of a bus, in 1962, parish dinners were begun. There are now two dinners each year. At the Spring and Fall dinners, homemade sausage is the main attraction. These dinners (along with Lenten fish fry's) contribute greatly to the financial support and social life of the parish.

Following the Second Vatican Council, in the spring of 1966, the church was remodeled and redecorated, according to a commission given to Brother Joseph, OSB, of the former St. Pius X Monastery, then located in Pevely, Missouri. In August 1966, Father Bromschwig was transferred to Holy Trinity Parish in St. Louis. He was succeeded by Father James Komaska as Administrator of the parish and of St. Dominic High School.

A picnic building was planned in the summer of 1968. With the help of pledges from the parishioners, and labor supplied by them, the building was completed in the fall of 1969, without incurring any debt.

In June, 1979, Father Komaska was transferred to St. Jerome Parish in North St. Louis County. Father Charles Burgoon was appointed Administrator for both the parish and St. Dominic High School. Due to the success of the festivals as well as the need for more Parish School of Religion classroom space, an addition to the picnic hall was begun in July, 1979, and completed in February, 1980. PSR classes were moved to the new facility at that time.

In June, 1982, Father Burgoon was transferred to St. Gregory Parish in St. Ann, and Father Wenceslaus Klaric came from St. Gregory's to Immaculate Heart of Mary to serve as the first full-time pastor. At this time, St. Charles County experienced a tremendous building and population boom, and by the time Father Klaric died, on August 26, 1992, the parish had grown to approximately 290 families. The Parish School of Religion had grown to about 130 children.

For many years our parish was blessed with Vincentian Fathers assisting us with weekend Masses. When it was no longer possible for them to help, for one year, priests from Kenrick-Glennon Seminary helped on weekends. However, since they were no longer able to assist, and it was impossible to obtain "regular" weekend help, the decision was made to transform the "front", or "new", hall into a Church Hall, for weekend worship. The five Masses formerly held in our 100 seat church were dropped to three, with the Church Hall being able to seat over 250 people. On July 5 and 6, 1997, the Church Hall was inaugurated as our weekend place of worship. Newly painted, carpeted, and air conditioned, it served as an adequate, if not ideal, place for worship. It soon became evident that the three Masses were not enough. With the increase of parishioners, and the popularity of the time, the 10:00 am Mass was quite often overly crowded. On Palm Sunday, 1998, a fourth Mass was added. The current schedule of four weekend Masses should be sufficient for the near future.

In September, 1992, Father Joseph A. Weber was appointed as the pastor of Immaculate Heart of Mary. Aided by the Parish Council, Men's Club, and Marian Council, he instituted the Worship Commission, the Budget and Finance Committee, the Dinner Committee, the St. Vincent de Paul Society, Scouting Programs, Knights of Columbus, and Athletic Programs. In 1997 he launched a Capital Campaign to build a new church to accommodate our growing parish family.  Fr. Weber was reassigned to St. Andrew Parish, in Lemay, on July 24, 2001.

In July of 2001, the parish welcomed the Reverend Richard Stoltz, from St. Luke's Parish in St. Louis, as our new pastor.

On December 16, 2001, ground was broken for the new church, and active construction started on January 2, 2002. Able to hold up to 750 people, the beautiful new Church was dedicated on May 4, 2003. In 2004, a second Capital Campaign, "Continuing to Build the City of God", was begun to finish the lower level of the new church and to pay down our debt.  With new buildings and spaces come new names.  In 2009 Fr. Stoltz renamed the original hall "Founders Hall", in honor of the founding parishioners of Immaculate Heart of Mary Parish.  He also renamed the "little Church" St. Joseph's Chapel.

On February 22, 2009, the Dedication of the "Grand Hall" took place.  This was a special celebration, not only because the final phase of the Church building was completed, but because so many of our parishioners had contributed their time and talent, in addition to their treasure. Our Grand Hall is proof that IHM parishioners take the commitment to stewardship to heart.

Under the spiritual leadership and temporal guidance of  Father Richard Stoltz, our Parish grew in many ways, striving to fulfill three main goals that he set out for the parish when he came, Hospitality, Liturgy and Education.  At the January 2012 farewell party for Fr. Stoltz, members of the parish renamed the IHM Grand Hall as the "Father Stoltz Grand Hall"-- a fitting tribute to one who prepared so many meals for us, both human (as a chef) and divine (as a priest).

Father Stoltz was transferred to St. Alban Roe parish in Wildwood, MO, and in January 2012, the parish welcomed its new pastor, Fr. Tom Miller, a native of Elsberry, MO and former pastor at Epiphany Parish in St. Louis. Under his pastoral guidance the parish embarked on a capital campaign to finally pay off the parish loan.  It was a great success, not only in the pledges received, but also in the early payoff of our loan in 2016, making us debt-free after 20 years!

It is the hope of all our people that the strong faith of past generations will guide our future... as it rests in the Hands of the Almighty. May God bless us as we seek to serve Him in the future!  Let's make the sign of the cross slowly as we seek the Lord's blessing and protection as we say, "Glory be to the Father and to the Son, and to the Holy Spirit, as it was in the beginning, is now and will be forever. Amen.  Alleluia!"