October is one of two months which has a special association with Our Lady—the other being the month of May. October holds significance because the liturgical Feast of Our Lady of the Rosary is celebrated each year on 7 October. This feast was established to honour the Blessed Virgin Mary in gratitude for the protection she gives the Church in answer to the praying of the Rosary by the faithful.

According to tradition, the Rosary as a form of prayer was given to St Dominic (1170-1221) by Our Blessed Lady. 
It developed as an alternative to the Divine Office for those who were illiterate, whereby the 150 Psalms of the Divine Office were replaced with 150 Hail Marys. These 150 Hail Marys were subsequently divided into fifteen decades in the fourteenth century, with each decade referring to an event in the lives of Jesus and Mary.

The practice of dedicating the whole month of October to Mary and the Rosary developed towards the end of the nineteenth century, with Pope Leo XIII being a strong advocate of the value of reciting the Rosary.  Subsequent popes continued to encourage the faithful to recite the Rosary, and in 2002 Pope John Paul II added five additional decades which highlight events in Jesus' public ministry.