By its history and context, Rerum Novarum was first an encyclical to the West but Europe in particular. The social question in general and for workers in particular had shaken Western Europe since the late eighteenth century. Before Leo XIII, Cardinal Manning in Manchester, Cardinal Bonald in Lyon (for the United States, one should cite also Cardinal Gibbons), and Bishop Ketteler in Mainz judged “critically the economic structures responsible for proletarianization.” The great presence of Bishop Ketteler played a special role in the genesis of the encyclical. He inspired the Catholic conscience, including the masters of French social Catholicism, such as René de La Tour du Pin, Albert de Mun, and Léon Harmel who led a pilgrimage of thousands of workers to meet Leo XIII. The encyclical appeared at the end of a long century of misery and the exploitation of workers that was especially appalling for children. It was time for the Church to speak.
Dominique Rey, "The Meaning of Rerum Novarum for Western Europe Today," Journal of Markets & Morality 19, no. 2 (Fall 2016): 431-446