The only thing worth more than the slaves in the American economy of the 1850s was the land itself, and no one can really put a dollar value on all of the land of North America.

十九世纪五十年代的美国经济中,唯一价值超过奴隶的就是土地,而且没有人能够真正对,美国北部的土地进行估值

耶鲁公开课 - 美国内战与重建课程节选