What made standard oil a monopoly?

Standard Oil became a monopoly primarily through aggressive business practices, such as predatory pricing and strategic acquisitions that eliminated competition. Founded by John D. Rockefeller in 1870, the company gained control over a vast majority of the oil refining industry in the United States, effectively dominating the market. Its extensive network of pipelines and distribution channels further solidified its market power, allowing it to dictate prices and limit competitors' access to resources. These actions led to public outcry and ultimately resulted in antitrust litigation, culminating in the company's breakup in 1911.