Leo John Dehon was born in France in 1843. When he entered the seminary, he had already completed his studies as a civil lawyer.
Leo's first appointment was to an industrial town called St. Quentin with 30,000 parishioners. He recognized immediately that working conditions, housing and the quality of the factory workers' lives were appalling, as they lived in dire poverty. Moreover, they felt that the church didn't care about them. Leo set about to organize help and establish support systems for the parents and youth of poor families. Much of his priestly life was dedicated to bridging the gap between the church and the working poor.
Leo began to experience the call to live as a member of a religious community. He became increasingly aware of God's love flooding into his life through the person of Jesus, and he wanted to return that love in the most genuine way he could.He became convinced that it was to be a community of men who were committed to cultivating a deep love for Christ, through lives of self-surrender to God and service to people, especially to the poorest of society. Leo felt that such a group was needed to respond to the serious wrong in society's relationship with God and its abusive treatment of the poor and defenceless.
On the Feast of Sacred Heart in 1878 Leo Dehon professed his vows and founded the Priests of the Sacred Heart.
The local bishop asked the new community to establish and take responsibility for a new school: St. John's College. Soon education, ministry to poor labourers, and apostolic service in foreign missions became the focus of the growing community. Leo guided the growth of the community in such a way as to make it clear that this religious brotherhood was to be a life of active ministry with a profound relationship with God fed by prayer and the Eucharist.
Leo died in Brussels, Belgium, on August 12, 1925.
On April 8, 1997, Pope John Paul II declared him "Venerable". It is a significant stage in the long process toward canonization.