The early morning whistles blew across Pennsylvania’s coal country on May 12, 1902. But 147,000 men and boys didn’t heed the summons to the mines. On that Monday they wouldn’t dig out the anthracite coal, or cart it above ground, or break it into pieces suitable for the homes, offices, factories, and railroads that depended on it. They wouldn’t show up on May 13 or the 162 days that followed.

The anthracite coal miners worked in dangerous conditions, were often underpaid and in debt, and knew the hardship to come. The coal barons expected to wait them out. The strike that began that May would become one of the greatest labor actions in American history. It was a confrontation between a past where power was concentrated and a future where it was shared, and it would define the presidency of Theodore Roosevelt.

Roosevelt had taken office eight months earlier, in September 1901, after President William McKinley was assassinated by a disgruntled former factory worker. Roosevelt retained McKinley’s cabinet, promised to follow his business-friendly policies, and accepted the counsel of McKinley’s closest advisor to “go slow.”

But not for long. In February 1902, Roosevelt’s attorney general, Philander Knox, announced that the Department of Justice would prosecute the railroad company just created by the nation’s most influential businessman for violating the Sherman Antitrust Act. Northern Securities, a combination of three rail lines that dominated the Northwest, was now the second-biggest company in the world and its owner, John Pierpont Morgan, already controlled the biggest: United States Steel.

As the 20th century began, few people could avoid everyday encounters with monopolies: businesses trading oil, salt, meat, whiskey, starch, coal, tin, copper, lead, oil cloth, rope, school slate, envelopes and paper bags were pooled and combined and rarely held to account. Once settled in his new job, Roosevelt aimed to guarantee that, as America’s prosperity took hold, the laws applied to the country’s elite and its poor alike—to its agitated laborers, and its heralded capitalists. He wanted to assert the primacy of government over business.