The parish traces its history back to 1856, when population growth in the city of Davenport led the Dubuque Diocese to establish a new parish on top of the hill on the east side of Davenport.
Antoine and Marguerite LeClaire donated the parcel of land and funds to build the church.
Before this time parishioners attended St. Anthony's Church in downtown Davenport.

On June 29, 1856, Bishop Mathias Loras of Dubuque laid the cornerstone for the church.
Antoine LeClaire directed the construction of the church, which was named St. Margaret (or sometimes listed as St. Marguerite) in honor of St. Margaret of Scotland and Marguerite LeClaire.
The church was built of red brick in the Romanesque Revival style.
A frame rectory was built next to the church.
It was moved to the back of the parish property in 1859 and a brick rectory replaced it.
Once again Antoine LeClaire provided the money.
A year later a brick building was built on the west side of the church.
It was meant to be a part of a future expansion of the church.
The upper floor housed a Sodality Chapel and the main floor included a sacristy and school rooms for boys.

The Rev. Andrew Trevis was named the parish's first pastor.
In 1857 the Rev. Henry Cosgrove was assigned to St. Margaret's after his ordination and became the pastor in 1861.
 He was destined to spend the rest of his life associated with the parish.

During the American Civil War from 1861–1865 the Union Army established a headquarters in Davenport.
There were five army camps in the city and four of them were within St. Margaret's parish boundaries.
Undoubtedly, this affected the parish and the pastor's ministry.
 After the war an addition was made to the church building in 1866 forming a wing on the right side of the original church structure.
The 1860 building on the left side was also incorporated into the church.
An unusual feature of the church was that the roofline of the addition was higher than that of the original church.

An arsonist, who was never caught, set fire to the church on May 2, 1873.
Damage was limited to the altar.
A new altar was installed later that year with a painting of St. Margaret that now hangs in the present cathedral.
Another criminal act affected the parish in the early hours of the morning of March 31, 1878, when two gunmen and a third individual attempted to rob the parish of a collection from the Forty Hours' Devotion the night before.
One of the gunman shot at, but missed, Father Cosgrove who was still in bed.
They escaped without the collection, but with jewelry from the housekeeper's daughter.
A $3,000 reward was offered and the three men were caught and sentenced to prison terms at the Anamosa State Penitentiary.

On May 8, 1881, Pope Leo XIII established the Diocese of Davenport.
The Very Rev. John McMullen, the vicar general of the Archdiocese of Chicago and rector of Holy Name Cathedral, was chosen as the first bishop, and he made St. Margaret's his cathedral.
A reception for him was held on July 30, 1881.
A platform was built on the front of the church for the occasion.
Bishop McMullen celebrated Mass for the first time in St. Margaret's Cathedral the following day.
Father Cosgrove became the cathedral's rector and the vicar general of the diocese.

Bishop McMullen died on July 4, 1883, and was buried below the high altar of St. Margaret's.
On July 11, 1884, Father Cosgrove was named by Pope Leo XIII to replace McMullen as Bishop of Davenport.
He was the first of three rectors/pastors to be named a bishop.
The parish traces its history back to 1856, when population growth in the city of Davenport led the Dubuque Diocese to establish a new parish on top of the hill on the east side of Davenport. Antoine and Marguerite LeClaire donated the parcel of land and funds to build the church. Before this time parishioners attended St. Anthony's Church in downtown Davenport.
On June 29, 1856, Bishop Mathias Loras of Dubuque laid the cornerstone for the church. Antoine LeClaire directed the construction of the church, which was named St. Margaret (or sometimes listed as St. Marguerite) in honor of St. Margaret of Scotland and Marguerite LeClaire. The church was built of red brick in the Romanesque Revival style. A frame rectory was built next to the church. It was moved to the back of the parish property in 1859 and a brick rectory replaced it. Once again Antoine LeClaire provided the money. A year later a brick building was built on the west side of the church. It was meant to be a part of a future expansion of the church. The upper floor housed a Sodality Chapel and the main floor included a sacristy and school rooms for boys.
The Rev. Andrew Trevis was named the parish's first pastor. In 1857 the Rev. Henry Cosgrove was assigned to St. Margaret's after his ordination and became the pastor in 1861.  He was destined to spend the rest of his life associated with the parish.
During the American Civil War from 1861–1865 the Union Army established a headquarters in Davenport. There were five army camps in the city and four of them were within St. Margaret's parish boundaries. Undoubtedly, this affected the parish and the pastor's ministry.  After the war an addition was made to the church building in 1866 forming a wing on the right side of the original church structure. The 1860 building on the left side was also incorporated into the church. An unusual feature of the church was that the roofline of the addition was higher than that of the original church.
An arsonist, who was never caught, set fire to the church on May 2, 1873. Damage was limited to the altar. A new altar was installed later that year with a painting of St. Margaret that now hangs in the present cathedral. Another criminal act affected the parish in the early hours of the morning of March 31, 1878, when two gunmen and a third individual attempted to rob the parish of a collection from the Forty Hours' Devotion the night before. One of the gunman shot at, but missed, Father Cosgrove who was still in bed. They escaped without the collection, but with jewelry from the housekeeper's daughter. A $3,000 reward was offered and the three men were caught and sentenced to prison terms at the Anamosa State Penitentiary.
On May 8, 1881, Pope Leo XIII established the Diocese of Davenport. The Very Rev. John McMullen, the vicar general of the Archdiocese of Chicago and rector of Holy Name Cathedral, was chosen as the first bishop, and he made St. Margaret's his cathedral. A reception for him was held on July 30, 1881. A platform was built on the front of the church for the occasion. Bishop McMullen celebrated Mass for the first time in St. Margaret's Cathedral the following day. Father Cosgrove became the cathedral's rector and the vicar general of the diocese.
Bishop McMullen died on July 4, 1883, and was buried below the high altar of St. Margaret's. On July 11, 1884, Father Cosgrove was named by Pope Leo XIII to replace McMullen as Bishop of Davenport. He was the first of three rectors/pastors to be named a bishop.
Sacred Heart Cathedral (Davenport, Iowa)