A list of Massachusetts based companies. Many well known Massachusetts companies have been included. While this list isn't definitive, these are most of the top businesses in the state of Massachusetts. As a country, the United States has encouraged entrepreneurship throughout much of its history.What companies have headquarters in Massachusetts? The state of Massachusetts is no exception to this rule, and new businesses are started in Massachusetts 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 Massachusetts.