How did john d. rockefeller horizontally integrate his monopoly in 1800?

Rockefeller used the size of his company Standard Oil to negotiate preferential rates with railroad companies to transfer his oil in the refinement process. By gaining the upper hand in transportation costs, he was able to horizontally integrate his competitors into his firm working to establish a monopoly in the American oil industry. 

They were constantly being overlooked as a people and were being controlled by people who weren't really native to their homeland.