
It was not the first strike called by the UMWA. The union had been successful in a strike called in 1897 for those who mined soft-coal (bituminous coal) in the Midwest. The union won significant wage increases for its members, causing the UMWA to grow in size from 10,000 to 115,000 members. A number of small strikes took place in the region where anthracite was mined from 1899 to 1901, and the union organinized more workers as a result.
The UMWA's success led to resistance from mine operators, who organized their own concerted and united front against the union. The owners refused to meet with or to arbitrate with the union. As a result, the union called a strike which began on September 17, 1900. Even union leaders were surprised with the support it received from miners, many of whom were from different nationalities and ethnicities, but who united in support of the union.
Republican Party Senator Mark Hanna of Ohio was both the owner of bituminous coal mines (though not ones involved in the strike), and a close friend of the sitting President, William McKinley. He attempted to resolve the strike, motivated by the fact that it occurred less than two months before the presidential election. He attempted to get the National Civic Federation to bring labor and capital representatives together. He asked industrialist J. P. Morgan to try to convince mine owners that a strike would hurt the reelection changes for McKinley. Hanna convinced the owners to agree to a wage increase and a procedure for the strikers to settle their grievances. But the mine owners balked on the question of formal recognition of the UMWA as the bargaining representative of the workers. The union took its modest gains and dropped its demand for recognition.
In 1902, the UMWA continued to press for recognition as the bargaining agent for the minors. But the mine owners continued to harbor bad feelings against the union from the 1900 strike. No one looked forward to another strike as 150,000 miners counted on their wages and millions of city dwellers counted on their coal delivery to heat their homes. John Mitchell, who was President of the UMWA, proposed mediation through the National Civic Federation, a group of employers who believed in the concept of collective bargaining as a means of resolving labor disputes. In the alternative, Mitchell proposed that a committee of clergymen produce a report on conditions in the coalfields. George Baer, President of the Philadelphia and Reading Railroad, who spoke for the mine owners, rejected both proposals.
On May 12, 1902, the anthracite miners held a vote in Scranton, Pennsylvania. They voted to go out on strike. The maintenance employees, who did not face the risks of underground work, walked out on June 2. The union had the support of roughly eighty percent of the workers in this region, or more than 100,000 strikers. Some 30,000 left to look for work in the Midwestern bituminous mines. Another 10,000 men returned to Europe. The strike led to violence between the strikers on one side and strikebreakers, the Pennsylvania National Guard, local police, and hired detective agencies on the other.
Theodore Roosevelt was now President and he refused to be a mere spectator to the dispute. On June 8, 1902 he asked his Commissioner of Labor, Carroll D. Wright, to investigate the strike. Wright reported back and proposed reforms that included a nine-hour day on an experimental basis and limited collective bargaining. Roosevelt decided not to release the report, concerned that doing so would make it appear that he was on the side of the union.
The owners continued to refuse to negotiate with the union. George Baer took a paternalistic approach, claiming that the interests of the miners were better protected, in his words, "not by the labor agitators, but by the Christian men to whom God in His infinite wisdom has given the control of the property interests of the country." The union used this letter to try to sway public opinion in their favor.
Roosevelt continued to contemplate intervention. He was advised by his Attorney General, Philander Knox, that he had no authority to do so. Mark Hanna and others leading Republicans were concerned about the political implications if the strike dragged on into winter, when the need for anthracite was greatest. Roosevelt told Hanna, "A coal famine in the winter is an ugly thing and I fear we shall see terrible suffering and grave disaster."
Roosevelt convened a conference of representatives of government, labor, and management on October 3, 1902. The union took offense to the notion of even holding of a meeting. The saw it as support for union recognition, something they opposed. They argued that strikers had killed at least twenty company supporters and they said that if Roosevelt planned to use the power of government, he should do so to protect those who supported the employers. They claimed that with proper protection, they could produce enough coal to end the fuel shortage. The owners continued to refuse to enter into any negotiations with the union.
The Governor of Pennsylvania sent in the National Guard to protect the mines and the men who were still working them. Roosevelt tried to persuade the union to end the strike with a promise that he would create a commission to study the causes of the strike and propose a solution. He said that he would use all of the authority of his office to bring about that solution. John Mitchell refused and his membership endorsed his decision by a near unanimous vote.
A drop in the supply of coal meant an increase in its price. At a time before the use of oil and electricity, there were no safe substitutes. The owners were not opposed to a moderately long strike because coal prices had been low and they had huge stockpiles which increased daily in value. It was illegal for the owners to conspire to shut down production, but if the miners went on strike, they could achieve the same result. The owners benefited from the strike, so they refused to recognize the union.
Roosevelt continued to convince the parties to agree to a mediated solution. He persuaded former president Grover Cleveland to join the commission he was creating. He also considered sending the U.S. Army to take over the coalfields. J.P. Morgan was the dominant figure in American finance at the time and had played a role in resolving the 1900 strike. He was affected by this strike as well, as the owner of the Reading Railroad, one of the largest employers of miners. At the urging of Secretary of War Elihu Root, Morgan proposed resolution through arbitration. He said that this would give allow the employers to negotiate through the commission and not directly with the union. The employers agreed on the condition that the five members of the commision be a military engineer, a mining engineer, a judge, an expert in the coal business, and an "eminent sociologist". The employers were willing to accept a union leader as the "eminent sociologist". Roosevelt appointed E. E. Clark, head of the railway conductors' union, as the "eminent sociologist." As a result of pressure from Catholic leaders, he added a sixth member, Catholic Bishop John Lancaster Spalding, and Commissioner Carroll Wright as the seventh member.
The strike ended of October 23, 1902. It had lasted for 163 days. The commissioners began its work the next day, touring the coal regions and reviewing data provided by Commissioner Wright about the cost of living in the coalfields. The commission held hearings in Scranton over the next three months, taking testimony from 558 witnesses, including 240 for the striking miners, 153 for nonunion mine workers, 154 for the operators, and 11 called by the Commission itself. Baer made the closing arguments for the coal operators, while lawyer Clarence Darrow did likewise for the workers.
The commissioners concluded that the worst cases presented at the hearing represented the minority of mining communities. They found that social conditions in mine communities were generally good, and miners were only partly justified in their claim that annual earnings were not sufficient to live on. The miners had asked for 20% wage increases, and most were given a 10% increase. The miners had asked for an eight-hour day and were awarded a nine-hour day instead of the standard ten hours prevailing at the time. Though the operators refused to recognize the UMWA, the commission created a six-man arbitration board, made up of equal numbers of labor and management representatives, with the power to settle labor disputes.

The conduct of the Coal and Iron Police during the strike led to the formation of the Pennsylvania State Police, on May 2, 1905. Senate Bill 278 was signed into law by Governor Samuel W. Pennypacker.
Organized labor saw the outcome as a victory for the UMWA and membership in other unions increased dramatically. Roosevelt was pleased with how the strike was successfully mediated through the intervention of the federal government. He called it an example of how his administration sought to provide a "Square Deal" for the working man, a phrase that Roosevelt used as a motto for his administration. There were no more major coal strikes until the 1920s.