Mason–Dixon LineyoudaoicibaDictYouDict[Mason–Dixon Line 词源字典]
"(In the US) the boundary between Maryland and Pennsylvania, taken as the northern limit of the slave-owning states before the abolition of slavery", Named after Charles Mason and Jeremiah Dixon, the 18th-century English astronomers who surveyed it in 1763–7.[Mason–Dixon Line etymology, Mason–Dixon Line origin, 英语词源]