the North's desire to create non-slave states in order to create a larger voting block in Congress (gosh, how similar that sounds to the liberal policies of today)Actually, it is exactly the opposite.
Liberal policies of today attempt to create a larger voting block in Congress by creating slaves- slaves to them and the government. Similarly, conservatives are trying to create a larger voting block in Congress by trying to stem that tide.
But in terms of the time before the Civil War, if you are trying to tell me that it was wrong of the North to desire to create non-slave states in order to create a larger voting block in Congress, I will say that sounds like persuing a reasonable reward for a just cause. Slavery was an abomination and was a blight on the tenets of liberty our nation was founded upon. And I will forever hold a grudge against those Confederate leaders, because it was their wrong-headed insistence on maintaining slavery that has forever damaged the cause of limited Federal government and states rights (the post-Civil War philosophical battle about the role of the Federal government has been lost because the issue of slavery drowns out everything else).
The matter was decided basically on the basis of population. The North won because their economic people-grinding machine allowed its grindees to vote. The Southern plantation system depended on the slaves' not voting.
The Irish immigrants in particular found out very quickly, in the first yellowjack outbreak in New Orleans, that Irishmen are constitutionally unsuited to surviving recurrent epidemics of malaria and yellowjack, and so they switched their emigration destinations to the Northern entry ports. German and other immigrants tended to favor northerly ports, too, as shown by their distribution pattern across the country. (The exception was Texas, where substantial numbers of Irish, Germans, Bohemians, Moravians, and German Jews settled both before and after the Civil War. Many roads around Houston are old farm roads that preserve the names of Jewish German farmers in the area: Gessner, Voss, Silber, Westheimer, Bingle, Beinhorn. But it was a small exception.)