### Issuance of Rerum Novarum **Date**: May 15, 1891 • **Location**: Rome, Italy Pope Leo XIII issued the encyclical Rerum novarum, which addressed the condition of the working classes and is considered to be the foundation of modern Catholic social teaching. Pope Leo XIII was head of the Catholic Church from 1878 until his death in 1903. He had the fourth-longest reign and third-longest verified reign of any pope, behind those of St. Peter, Pius IX, and John Paul II.

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