When Pope Pius IX went into exile at Gaeta in the Kingdom of the Two Sicilies (1849), he had as his companion Father Giovanni Merlini, third superior general of the Fathers of the Most Precious Blood. After they had arrived at Gaeta, Don Merlini suggested that His Holiness make a vow to extend the feast of the Precious Blood to the entire Church, if he would again recover possession of the Papal States. The Pope took the matter under consideration, but a few days later, on 30 June 1849, the day the French army conquered Rome and the insurgents of the Roman Republic capitulated, he sent his domestic prelate Joseph Stella to Father Merlini with the message: "The pope does not deem it expedient to bind himself by a vow; instead His Holiness is pleased to extend the feast immediately to all Christendom."
On August 10th of the same year, he officially included the feast of the Most Precious Blood of Our Lord Jesus Christ in the General Roman Calendar for celebration on the first Sunday in July, the first Sunday after 30 June, the anniversary of the liberation of the city of Rome from the insurgents.
In reducing the number of feasts fixed for Sundays, Pope Pius X assigned the date of July 1st to this feast. Ecclesia Vetusta Catholica always celebrates this feast day on July 1st despite it being downgraded by the Second Vatican Council.
In 1933, Pope Pius XI raised the feast to the rank of Double of the 1st Class to mark the 1900th anniversary of Our Lord's death.