But, how did the standard depth of six feet for graves get set?
The origins of the standard came from a 1665 plague outbreak in England. As the disease swept the country, the mayor of London laid down the law about how to deal with the bodies to avoid further infections. Among his specifications—made in “Orders Conceived and Published by the Lord Major and Aldermen of the City of London, Concerning the Infection of the Plague”—was that “all the graves shall be at least six feet deep.”
However, modern American burial laws vary from state to state, and many states simply require a minimum of 18 inches of soil on top of the casket or burial vault (or two feet of soil if the body is not enclosed in anything).