Rockefeller did this by killing off competitors one by one until only his company, Standard Oil, remained with a monopoly.
Rockefeller referred to the American Beauty rose as something that could only be produced by killing all the other buds that grew up around it. He said that killing all those buds allowed the one American Beauty rose to flourish. He drew an analogy between this and business. Businesses could only become truly great (he argued) if they killed off all their competitors. This is exactly what Rockefeller did in his own business life.