St. Mary is the second oldest Catholic church in Rockford, built when the area was still under the territory of the Archdiocese of Chicago.

The cornerstone was laid in July 1886 by Chicago Archbishop Patrick A. Feehan, and it was completed in 1887, dedicated in October that year. Its first pastor, Father Edward Murphy, opened a parish school in the church basement, staffed by Sinsinawa Dominican sisters. The parish’s third pastor, Father McMahon was installed in 1892. He built a convent for the teaching sisters, a school building adjacent to the church, and in 1913 the present rectory.

In 1906 Dominican Sisters of Blauvelt, NY, taught at the school, followed in 1912 by Sisters of Loretto.

In 1928, a grotto dedicated to Our Lady of Lourdes was constructed. Its cave-like interior houses a simple low altar and two shrines to St. Bernadette/Our Lady of Lourdes and to St. Therese of Lisieux. It continues to be open for prayer on weekdays at specific times.

In 1933, the church’s care was given to the Augustinian priests who served the parish for the next 64 years. A 1962 fire destroyed the church’s interior, particularly in the back including the choir loft, organ, roof, bell tower, pews, and confessionals. It was, says the parish website, “restored to only a portion of its former elegance.” The church interior was redecorated in 1973.

From 1968-1974, sisters from the Philippines affiliated with the Augustinian Order taught at St. Mary School, which was closed with their departure.

In October 1997, St. Mary was officially given to the pastoral care of the Institute of Christ the King Sovereign Priest. In early 2007, Bishop Thomas G. Doran erected St. Mary Shrine as a “public oratory.” Catholics from all locations may attend the Oratory, forming a Latin Rite Faith Community and receiving the sacraments according to the 1962 rubrics.

Since then, renovations have included refurbishing the sanctuary, re-leading and reconditioning the stained-glass windows; also the original altar rail was restored and two side altars were constructed and dedicated to Our Lady of the Sacred Heart and to St. Joseph.