St. Bernard was established in August of 1919. The origin of the parish can be traced to the opening of a street car tunnel through Mt. Washington in 1904. This event eased travel between the South Hills and downtown and made possible the growth of population in the South Hills. In the spring of 1919, a group of Catholics living in Dormont petitioned the bishop for a new parish. The bishop agreed and the parish covering Mt. Lebanon and part of Dormont was formed.
The first Mass of the new parish was celebrated on August 31, 1919, in the second floor of a privately owned carriage house. On December 31, 1919, the parish purchased land to build a parish plant. The purchased property included a brick house which was converted to a rectory and temporary church. The last Mass in the carriage house was celebrated on January 11, 1920, and the next day the first Mass was celebrated in the new church.
However, it soon became obvious that it was impractical to try to use the house as a church and rectory. The parish purchased a pre-fabricated building on April 11, 1920, which they dubbed the portable church. This building was 200 feet long, and 20 feet wide and was dedicated on June 27, 1920.
The congregation continued to grow, spurred on by the opening of the Liberty Tubes in 1924. It quickly outgrew the portable church. On August 20, 1924, the parish broke ground for a new school which would also include a temporary church. The cornerstone of the new building was laid on April 12, 1925, and the school opened on September 8, 1925. The ground level of the school served as the church and the upper two levels contained classrooms. The building was dedicated on January 31, 1926. Shortly afterwards, the portable church was donated to the new St. Joan of Arc mission in Library. As the school attendance continued to grow, the parish soon needed the church space in the school building for classrooms. In 1933, the bishop gave the parish permission to build the basement of the new church up to the floor level of the superstructure. Permission to build the superstructure was withheld because of the depression. Work on the basement began in 1934 and the basement chapel was dedicated on December 16, 1934.
In 1938, the bishop granted the parish permission to complete the church. However, construction did not start until January of 1942. The first Mass in the still unfinished church was celebrated on Palm Sunday of 1947. Work on the church continued through the rest of the 1940's and all through the 1950's and 1960's. Not until June 23, 1969, did the pastor declare the church completed.
Work continued on the church after that. In the early 1970's the church suffered water damage that was repaired in 1973 and 1974. In 1982, the lower church was remodeled into a parish hall.
