The Hanover Insurance Group, Inc. is an insurance company based in Worcester, Massachusetts. It was the original name of a property-liability insurance firm established in 1852, and it remained a publicly traded company under that name until the early 1990s, when it changed its name to Allmerica Property & Casualty Companies. In 1996 it spun off Allmerica Financial Corporation as a property and casualty insurance and financial services holding company, which then bought out the original firm, and grew to become one of the 500 largest publicly traded companies of the United States. Wikipedia