Fr. Leonard was born in Buffalo, New York, May 15, 1861. Later his family moved to Springfield, Massachusetts. He made his classical studies at Ottawa College, his philosophical course at the University of Toronto and attended the grand seminary, Montreal, Canada, where he was ordained to the priesthood December 17, 1892 by the Archbishop Edouard C. Fabre.
Following his ordination to the arch diocese of Boston, Fr. Leonard was named assistant at St. Patrick’s Church, Lowell, Massachusetts where he served eight years. His second curacy was at St. Joseph’s Church in Pittsfield, Massachusetts where he served from 1900 to 1913.
As the population of Pittsfield increased, it became clear in the early 1900s that a new parish was needed for the accommodation for the people of western section of the city. Bishop Thomas D. Beaven, Bishop of the Springfield diocese, purchased land on West Street between South John Street and Onota Street for a chapel for the new parish, to be called St. Mark’s. the wooden building was erected on the north –west corner of the property facing Onota Street, leaving room for a larger, more permanent church at a later date.
Reverend Michael J. Leonard became the first pastor of the new parish. With Father Florence Lane as his first assistant, Father Leonard held services in the new building in May 1913. The formal dedication was held the following year with Bishop Beaven officiating.
Under his leadership the congregation tripled in numbers in ensuing years. Fr. Leonard was known as the “convert priest” from the number who were led into the church through is instructions. Realizing the need for expansion in 1929, the parishioners had outgrown this space and plans were put underway to build a larger, more appropriate house of worship. With immense support from the congregation and under the leadership of Fr. Leonard, the new St. Mark’s was built on West Street on what was called the Albro Tract. It was dedicated amid much pomp in May 1932, with the Most Reverend Thomas M. O’Leary, Bishop of Springfield, celebrating the liturgy for the occasion. With a special concert, the majestic Kilgen organ was also dedicated. At the first midnight Mass in the new church, the beautiful stained –glass window above the main alter was unveiled. This was followed a year later with the dedication for our Lady of Lourdes Shrine on the West Lawn of the church.
Fr. Leonard celebrated his Golden Jubilee in December 17, 1942 and died at the age of 94, October 25, 1955, after a short illness, he spent 55 years of his life in Pittsfield, a remarkable 42 of these years as pastor of St. Mark’s Church.