King Coal by Upton Sinclair

Olson was eager to win Hal, and went on to tell all the secrets of his work. He sought men who believed in unions, and were willing to take the risk of trying to convert others. In each place he visited he would get a group together, and would arrange some way to communicate with them after he left, smuggling in propaganda literature for distribution. So there would be the nucleus of an organisation. In a year or two they would have such a nucleus in every camp, and then they would be ready to come into the open, calling meetings in the towns, and in places in the canyons to which the miners would flock. So the flame of revolt would leap up; men would join the movement faster than the companies could get rid of them, and they would make a demand for their rights, backed with the threat of a strike throughout the entire district.

"You understand," added Olson, "we have a legal right to organise -- even though the bosses disapprove. You need not stand back on that score."