Mining exploration in northwestern Québec was the work of prospectors from Ontario. In the 1910s many of them scoured the area in canoes, looking for new deposits. Edmund Horne was one of these prospectors looking for gold. In 1911 he made his first trip to the area where Rouyn now stands. He returned in 1914 and 1917. In the early 1920s, his flair and perseverance led him to discover what turned out to be the largest ore deposit in the region. This find resulted in the creation of Noranda Mines Limited in 1922. The construction of the Horne Mine and its copper smelter began in 1925. Two years later, production began.

Edmund Horne almost certainly had not the slightest inkling of the impact his discovery would have on the course of history. It gave rise to a company that subsequently became a multinational venture and also led to the founding of two cities, Rouyn and Noranda, which merged in 1986. These two cities were destined to become the meeting point between two regions, the Abitibi and the Témiscamingue, which until then had been two distinct entities.