This will upset those living in liberal fantasy land, but on fiscal issues it was 1856. Period. The GOP has always been a pro-business party, and I honestly find it 100% revisionist and biased to call defending slavery (as Southern Democrats did) socially conservative and trying to tie that to conservatism of today, while also completely ignoring that some of the fiercest abolitionists were from devoutly conservative Christian denominations like the Quakers. The Second Great Awakening and the explosion of moralism that followed (something Democrats still mock Republicans for today) did a heck of a lot more to advance anti-slavery sentiment than this revisionist notion that the charge was led by these intellectual progressives of the day. When you throw in that the other main group that opposed slavery was the Northern business community, which argued it interfered with the ideal of a free market with free labor, it doesn't sound liberal or left wing at all to me ... I guess if you repeat something loud enough and often enough, it becomes accepted as truth.
There's some degree of truth to this, however, the Republican Party in the mid-19th century was composed of numerous factions. Some of them favoring a "small" government and an agrarian based economy. They were against a central bank, tariffs, and hell even a national currency. These were called the liberal Republicans and contained a lot of ex-Democrats. The other wing consisted of ex-Whigs who favored a central bank, corporate welfare and protectionism through tariffs.
You're correct in saying the Republican Party was always the party of big business (and those weren't often formed splinter groups such as Roosevelt's Bull Moose Party La Follette's progressives) and because the Democratic base for much of the 19th century were farmers and later a coalition of rural farmers and urban labor machines. Hardly the people you'd expect to support a party of big business. You're also correct in saying that people's religious beliefs via the Second Great Awakening were a main driving force behind the abolition movement.
For some local context, one of the reasons Rhode Island was such a bastion of the Republican Party in the 19th and early 20th century was due to it being a very wealthy industrialized state with numerous corporations in Providence.
