And in 1861 they were Big City Republicans. You say they can live anywhere, but for some reason they chose to live in or near very wealthy cities like New York, Los Angeles, Boston, Washington DC and Chicago.
A little research could produce a much longer list of major metropolitan areas which dominate the US economically.
For example, this listing shows nearly 400 US metropolitan areas, totaling 87% of all Americans.
Of those only about 15% live in the cities you list:
Some of the large metropolitan areas you forgot include:
All of these metropolitan areas have their own commercial, manufacturing and financial centers, not necessarily dependent on New Yorkers or anyone else.
Point is: your efforts here to equate specific geography (i.e., "Northeasterners") with political wickedness are just ridiculous, and you should give it up.