How did Rockefeller use horizontal integration to build his impire?

Rockefeller was a very good business man who some considered to be a robber baron and others thought he was a captain of industry. Basically he wanted to become the (or monopoly) that way he could charge what ever prices he wanted. The biggest reason that he got as rich as he did was because he made a deal with a railroad company to transport his oil for a cheaper price and he would give the railroad some of the profit. Since other businesses didn't have deals like Rockefeller, his oil was cheaper so many people purchased his putting other oil companies out of business. This allowed him to rise to the top of the oil industry.

Well, to be more accurate, he built every oil field in the world except 2, which were built by Britain. His company, Standard Oil had NO competition. And to be more precise, he didn't use horizontal integration, he used verticle integration.