There, he joined the United Mine Workers of America, and in 1896, he was elected as the full-time president of the union's District Number 5.[1] The following year, he led a successful strike, during which he was arrested while leading a march.[2] In 1898, Dolan stood to become national vice-president of the union, but was defeated by John Mitchell.[3]
By 1906, Dolan was regarded as a conservative in the movement, opposed to strikes.[4] That year, he denounced Mitchell, who was by then the president of the union. He claimed that Mitchell had held a grudge against him since 1898, that Mitchell's tactics were poor, and that Mitchell had acted in an underhand manner, trying to undermine Dolan.[3] Dolan announced that he would not campaign for re-election as district president, and that he would continue in the post whatever the election result was.[5] He was defeated, but attended the annual district conference, and attempted to call it to order. The meeting unanimously moved to expel him, but he refused to leave until physically removed from the hall.[6]