A “Black Maria” is a police van for the conveyance of prisoners.
Tradition says that the original, in Boston, Massachusetts, in the early 1800’s, was named after an African American, Maria Lee, but known as “Black Maria,” who ran a lodging house for sailors, but who co-operated with the police in the arrest of any lodger who became unruly or violated the law.
It is not known when the first van acquired the name, but a Boston paper of 1847 tells of “a new Black Maria” being put into service.