Culture and climate
Brandeis historian David Hackett Fischer pointed out in his famous Albion's Seed that racial differences had an enormous impact on the history of America. He notes that the cold climate of colonial Massachusetts
"proved to be exceptionally dangerous to immigrants from tropical Africa, who suffered severely from pulmonary infections in New England winters. Black death rates in colonial Massachusetts were twice as high as whites' - a pattern very different from Virginia where mortality rates for the two races were not so far apart, and still more different from South Carolina where white death rates were higher than those of blacks. So high was mortality among African immigrants in New England that race slavery was not viable on a large scale, despite many attempts to introduce it. Slavery was not impossible in this region, but the human and material costs were higher than many wished to pay. A labor system which was fundamentally hostile to the Puritan ethos of New England was kept at bay partly by the climate."
Not surprisingly, in the 19th Century, Massachusetts became the home of abolitionism. South Carolina became the home of secession.