The Sherman Antitrust Act

The Standard Oil Company (1870-1911) was the largest petroleum company in the world, and its success made its co-founder and chairman, John D. Rockefeller, among the wealthiest Americans of all time and among the richest people in modern history. The self-made billionaire was the perfect target for government to step "in all fairness" to split the company up into 43 companies of historical confusion by the Sherman Antitrust Act of 1911. 

The 2022 chart above shows the break up of Standard Oil