St. Peter was founded in 1821, the first parish in Butler County. Originally, the parish was a territorial parish. The origin of the parish can be traced to the arrival of Irish immigrants to the area beginning in 1795. For the next ten years, the few Catholics in the area had to content themselves with an occasional visit from traveling missionaries or priests passing through the area on their way elsewhere. When St. Patrick in Sugar Creek was founded in 1806, that parish took responsibility for the Catholics of Butler.
By 1821, enough Catholics had moved into the area to make the organization of a parish practical. Plans to build a church were drawn up and work began that year. St. Peter church was built in 1822 and used by the congregation beginning in that year. However, it was not until 1834 that the church was completed and blessed.
During this time period, the German population of Butler began to grow. While the parish remained a mission of St. Patrick, German priests from Pittsburgh began making regular visits to St. Peter to minister to the Germans. In 1840, the parish became independent with the appointment of its first resident pastor. The Germans in the congregation continued to receive monthly visits from German priests from Pittsburgh, however.
By 1847, the existing church could no longer accommodate the growing congregation. In 1848 land was purchased for a new church. However, a dispute arose between the English speaking and German speaking members of the parish. Each wanted a church where they could worship in their own language. Bishop O'Connor offered an acceptable compromise by promising to send a pastor who could speak both languages. The cornerstone of the church was laid on August 6, 1848 and the new church was dedicated on October 14, 1849.
The conflict between the Germans and Irish eventually worked itself out. Most of the Germans lived in Butler itself while most of the Irish lived in the outskirts of the town. When St. Joseph, North Oakland was founded in 1847 and St. John, Coylesville was founded in 1853, many of the Irish members of St. Peter switched to those parishes. This made the congregation predominately German. With the founding of St. Paul, Butler in 1867, the remaining Irish left St. Peter to attend that parish and St. Peter became a German ethnic parish.
In 1889, the church was remodeled and enlarged. The church was renovated in 1899 with the installation of new glass windows and in 1924 with the installation of three new altars. In 1963 another major renovation to the church was made.
With the turn of the century, trends in the Diocese of Pittsburgh began to reveal a decline in Mass attendance and sacramental participation. At the same time, the number of priests available for parish ministry also began to decline.
To address these challenges, Bishop David Zubik announced on April 12, 2015 a new diocesan initiative, On Mission for The Church Alive!, a consultative strategic planning process designed to foster viable, sustainable and vibrant parishes. As part of this process, the Bishop, in consultation with the faithful, began to consider new models of parish life based on pastoral needs, financial and temporal resources and available clergy.
In 2018, following the period of consultation, parishes were grouped together and served by a single clergy team to eventually form one new parish.
During this transition period, St. Peter Parish remained an independent parish while sharing clergy and staff and eventually publishing a joint bulletin with the other parishes. This ended on July 1, 2021 when St. Peter Parish merged with St. Andrew Parish, Center Township; St. Fidelis of Sigmaringen Parish, Lyndora/Meridian and the Butler parishes of St. Peter and St. Michael the Archangel to form the new All Saints Parish. As part of the merger St. Peter Church remained open as part of the new parish.
