* John D. Rockefeller: Founder of Standard Oil, Rockefeller used horizontal integration to buy out or crush competitors, ultimately controlling 90% of the oil refining industry in the United States.
* Andrew Carnegie: Carnegie Steel used horizontal integration to acquire numerous steel mills, becoming the dominant steel producer in the United States.
* Cornelius Vanderbilt: Vanderbilt amassed a fortune through shipping and railroads, using horizontal integration to buy up competing steamship lines and railroads.
* Henry Ford: Ford Motor Company used horizontal integration to acquire smaller automobile companies and standardize production processes.
* Bill Gates: Microsoft, under Gates' leadership, used horizontal integration to acquire companies like Intuit, Hotmail, and Skype, expanding their reach in software and internet services.
These are just a few examples. Horizontal integration has been a popular business strategy for many centuries and continues to be used today.
It's important to note that horizontal integration can be controversial, as it can lead to monopolies and reduce competition in the marketplace.