The Story of Knock in East Mayo began on the 21st August 1879 when Our Lady, St. Joseph and St. John the Evangelist appeared at the south gable of Knock Parish Church.
The personal pilgrimage of Pope John Paul II in 1979, commemorating the centenary of the apparition, inspired an even greater devotion to the Shrine and endorsed the indelible seal of Vatican approval. Mother Teresa of Calcutta visited the Shrine in June of 1993. One and a half million pilgrims visit the Shrine annually.
On the evening of 21 August 1879, people whose ages ranged from five years to seventy-five and included men, women, teenagers,children, witnessed what they claimed was an apparition of Our Lady, St Joseph, and St John the Evangelist at the south gable end of the local small parish church, the Church of St John the Baptist. Behind them and a little to the left of St John was a plain altar. On the altar was a cross and a lamb (a traditional image of Jesus, as reflected in the religious phrase The Lamb of God) with adoring angels.
The Blessed Virgin Mary was described as being very beautiful, standing a few feet above the ground. She wore a white cloak, hanging in full folds and fastened at the neck. The crown appeared brilliant, and of a golden brightness, of a deeper hue, than the striking whiteness of the robe she wore; the upper parts of the crown appeared to be a series of sparkles, or glittering crosses. She was described as "deep in prayer", with her eyes raised to heaven, her hands raised to the shoulders or a little higher, the palms inclined slightly to the shoulders. Bridget Trench "went in immediately to kiss, as I thought, the feet of the Blessed Virgin; but I felt nothing in the embrace but the wall, and I wondered why I could not feel with my hands the figures which I had so plainly and so distinctly seen".
Altar sculpture at Knock, based on accounts of the apparition.St Joseph, also wearing white robes, stood on the Virgin's right hand. His head was bent forward from the shoulders towards the Blessed Virgin in respect.
St John the Evangelist stood to the left of the Blessed Virgin. He was dressed in a long robe and wore a mitre. He was partly turned away from the other figures. He appeared to be preaching and he held open a large book in his left hand.
To the left of St John was an altar with a lamb on it with a cross standing on the altar behind the lamb.
Those who witnessed the apparition stood in the pouring rain for up to two hours reciting the Rosary, a traditional Catholic prayer. When the apparition began there was good light, but although it then became very dark, witnesses could still see the figures very clearly - they appeared to be the colour of a bright whitish light. The apparition did not flicker or move in any way. The witnesses reported that the ground around the figures remained completely dry during the apparition although the wind was blowing from the south. Afterwards, however the ground at the gable became wet and the gable dark.