St. Columbkille was established in 1908. The origin of the parish can be traced back to the rise of the Imperial district in the 1890's and 1900's. The first Mass in Imperial might have been celebrated by Fr. Toner, in the home of Mr. Michael Duffy, in 1897. For the next eight years, the area was occasionally visited by priests from Bridgeville, Coraopolis, or Monaca. They would celebrate Mass in private homes or halls in Imperial. Fr. Martin Hughes, pastor of St. John in Monaca, was the first priest to visit Imperial regularly, and he established the Mission of St. Columbkille. This name was suggested to Fr. Hughes by the Conniff family, whose home parish in Scotland bore the same name. Later, when Fr. Hughes became pastor of St. Joseph in Coraopolis, he directed the construction of the first St. Columbkille church (made of timber). It was dedicated on August 15, 1905. From then on, Mass was celebrated monthly.
The success of the coal mining industry led to a population increase in Imperial, especially among Polish, Slovakian, and Slovenian immigrants. In 1908, a group of Catholics petitioned Bishop Richard Phelan to elevate the mission of St. Columbkille to the level of a parish, and grant them a resident pastor. The Bishop granted their request, and appointed Fr. Anthony Pniak as the first pastor. The new parish of St. Columbkille also oversaw the mission of Holy Trinity in Moon Run, until Holy Trinity became its own parish in 1944.
1942 was a pivotal year in St. Columbkille's history. This is when Fr. Ladislaus Kolakowski became pastor. He would serve at St. Columbkille until his death in 1965. In his 23 years of ministry at St. Columbkille, he oversaw the construction of most of the buildings on the campus (the church/faith formation building, the convent, and the rectory).
As St. Columbkille continued to grow, plans were made in 1943 to build a new church and a school. The original St. Columbkille church was razed in 1946. Mass was moved to Lyceum Hall (the old North Fayette Township school that the parish purchased in 1936). Although parishioners wanted to begin in earnest constructing a new church, a lack of funds delayed this project for several years. Construction finally began in 1952. The original plan was to build a traditional church building. However, at the suggestion of Bishop John Dearden, the plan was changed. Instead, the parish would build a combination church-school building. The new structure was dedicated on August 16, 1953. Thanks to the generosity of parishioners, it was built without incurring any debt. The hall, which had served as the temporary church, was later torn down in 1958.
The convent was completed in 1954, and dedicated on August 15 of that year. Its first inhabitants were the Sisters of the Third Order of St. Francis from Mt. Alvernia, Millvale. They are the Sisters who ran St. Columbkille School, which opened to grades 1 - 4 in September of 1954. Each year after that, a new grade was added until it went up to 8th grade in 1958. Enrollment began with 136 students in 1954. It peaked at over 400 students in the 1960's, and then declined. Unfortunately, the school was short lived. In 1971, the Sisters of St. Francis pulled out of St. Columbkille School. In its last year, the only Sister left was the principal (a Gilmary Sister). Declining enrollment, increasing debt, and rising costs led to the closing of the school in 1972, after 18 years in operation.
St. Columbkille Church was renovated in the mid-1960's. Additional improvements were made later. For example, the Altar of Repose was blessed in 1982, the Altar of Sacrifice was consecrated in 1985, and the Allen Organ was blessed in 1990. One thing most visitors notice is the pebble stone that is prominently placed in the front of the Atar. The stone comes from island of Iona (on the Western coast of Scotland), where St. Columba built his first monastery.
In April of 2015, an initiative called On Mission for the Church Alive! was begun to help parishes better provide for the needs of the faithful. This culminated in the merger of St. Columbkille Parish with the parishes of St. Alphonsus, St. Ann, St. Michael, Our Lady of Lourdes, and St. Patrick on July 1, 2020. This new parish, St. Isidore the Farmer, continues the good work of spreading the Gospel and building up the Kingdom of God.