How conservative were Northeastern Republicans before the 60's?

[Southern Senator North Carolina Yankee]

Depends on how you define Conservatism. Taft style conservatism was very popular in the rural parts of New England. The coastal and urban areas, comprising your urban middle class (they actually lived in the cities back then), business people and "old money blue bloods" would have been your Pro-business/commercial wing. You had the prohibitionists who wanted to perfect society by eliminating alcohol the same way their parents had seen abolition as a means to "perfect society". A lot of this was inspired/motivated by puritantical religious movements and such. People tend to not realize this because today's New England is a hotbed for atheism, agnosticism and so forth, but outside of the Unitarian and Univeralists, bulk of the Congragational and other mainline protestants back then were conservative, certainly by today's standards. Then of course you had the Catholics were also very conservative, if not necessarily so on banning beer and whiskey, but certainly on other things. That map of states laws on abortion from I think 1970 is very insightfull with regards to this.

Outside of the inner city ethnics and working class voters who were much more inclined to the Democrats, the Conservatism of the 1920's GOP did very well in the Northeast and it was seen again in 1946. The problem is that you see right after those periods (1930's in the former, 1948 in the later), what happened when the working class and ethnics got organized and turned out rather than sitting on their hands. Post 1896 (really post 1789 with the Federalists) the party was determined to be the business oriented one, and then post New Deal the party was determined to be the one for lesser gov't (in general, still okay for selected interests). You couldn't maintain a conservative GOP off just the Midwest and Northeast save for your wave years, because in most elections you would get decimated. That is why in the 1950's they began looking South again, reviving three decades old strategies from the 1928 campaign to tear those regions away from the Democratic party.

People can simplistically refer to parties flipping and so forth, but little stuff "that really mattered" (like whose interest is primarily served by the party) was changed. What did change was demographic reality of the Northeast and midwest caught with a party that no longer sought gov't to grow, when it ceased to advance commerical interests. Sure you had a moderate/liberal wing of the party that really got left behind between somewhere between the region shifts and restoration of partisanship along the new lines.