What was the core business that made the standers oil a horizontally integrated monopoly

Carnegie introduced the Bessemer process, which decreased the cost of production. What made Standard Oil a horizontal integration monopoly? It owned ninety percent of US oil refineries.

Explanation: Hope i helped you~! <\3

a historian researching the immigration policies of the early 1900s would expect a source written today,rather than in 1910 to :

( a ) be more interested in objective data and statistics.