Answer: An example of a Horizontally Integrated Company would be Standard Oil, owned at one time by John D. Rockefeller.
Explanation: Horizontal integration can be simply understood as a process of growing business by owning all companies involved in a certain step or level of production. Rockefeller horizontally integrated standard oil by purchasing all of the other oil refineries in the United States, and most others globally. This resulted in creating a monopoly on the oil market in the United States. Hope that helps!