A list of Maryland companies. Many well known Maryland companies have been included. While this list isn't definitive, these are most of the top businesses in the state of Maryland. As a country, the United States has encouraged entrepreneurship throughout much of its history. The state of Maryland is no exception to this rule, and new businesses are started in Maryland daily, ranging from corporations to LLCs to partnerships to sole proprietorships. This list, however, is mostly focused on the largest corporations in the state of Maryland.What are the companies headquartered in Maryland? You'll see some familiar names on this list, showing that the Terrapin State is a good place to set up a business.