The Economy of the North and Views of Slavery before the War to Prevent Southern Independence:
The economy of the North was mixed, but industrialism was dominant because of its wealth. If a farmer or craftsman had products for sale, the populations of the factory towns and industrial cities comprised his market. If a farmer or craftsman borrowed money, he probably borrowed it from the banking industry. The antebellum North was an industrial social system because industry determined the welfare of everybody: farmers, craftsmen, factory workers, industrial owners.
Abolitionists viewed slavery as a sin that must be abolished immediately without regard to how much such haste might disrupt society or throw many slaves (newly freed) out of a means of supporting themselves.
Many Northerners viewed slavery as a source of Southern political power. Since Southern politicians opposed import tariffs which subsidized industry at the expense of agriculture, and opposed spending tax dollars for improvements of harbors and for other subsidization of northern industry and trade, these Northerners opposed slavery. In fact, for this reason more than any other, most Northerners opposed slavery, though they were far less enthusiastic in their opposition than the abolitionists. Fanatical abolitionists were fewer in number than mildly anti-slavery Northerners.
Many northern working men opposed the abolitionists because the abolitionists refused to recognize northern labor problems. The laborers were concerned about their own plight and their own liberation. The abolitionists were concerned only about the plight and liberty of far-away slaves. Emancipation of the white man was the great labor objective, and working men's conventions rarely gave any consideration to the anti-slavery issue. There were instances of riots by factory workers against abolitionists because the factory workers feared that the end of slavery would result in many blacks migrating to the North to work in the factories. This would have brought the level of factory wages down. No doubt factory owners looked forward to this.
Horace Greely, a New York newspaper man, had a similar opinion: "If I am less troubled concerning slavery prevalent in Charleston or New Orleans, it is because I see so much slavery in New York which appears to claim my first efforts."
References for this answer:
Gara, Larry. 1975. "Slavery and the Slave Power: A Critical Distinction" in Robert P. Swierenga, ed., Beyond the Civil War Synthesis: Political Essays of the Civil War Era (1975), 295-308. [College-level reading.]
Rayback, Joseph G. 1943. "The American Workingman and the Antislavery Crusade," The Journal of Economic History, 3, 2 (Nov.), 152-163. [Senior high school and college-level reading.]
While there was a great deal of diversity and divergence in the North, one absolute which can be accepted was the growth of industrial mills and factories in the region. Since Slater stole the first designs from a factory and opened his own in America to Lowell establishing his entire town of factories, the rise of industry helped to distinguish it from the agrarian Southern counterpart. Factories and industrialization gave way to urbanization in the North, contributing to a more economically driven way of life in the Northern section of the United States. While abolitionism was present in the North, and while some individuals did drive the initiative for eliminating slavery, most of the North was driven by industry. The views of slavery, on behalf of factory owners, was a bit of envy as they wished for such a controlled labor pool as slaveowners in the South possessed. To this end, the Northern drive was to create such an economically dominant mode of reality that the institution of slavery could be "bought out" in a manner of speaking to ensure that the North would be the dominant economic force of the new nation.
The Northern economy was changing and growing before the Civil War, as the industrial revolution took hold and factories, producing mostly textiles, had spread across New England. The economy of the North was independent of slavery, though there was always a need for cheap labor. This was mostly performed by immigrants, but "free" blacks in the cities performed any number of menial tasks, and were heavily discriminated against, especially in cities like New York or Boston.
Northerners in general were racist, though their attitudes towards blacks were also not as harsh or well defined as their southern white countrymen's. Abolitionists were a small, although very loud, minority. They didn't want slavery to continue spreading, but not out of any sympathy or goodwill towards slaves.
The economy of the North before the war was quite mixed. There was, of course, still a lot of agriculture. There was also quite a bit of manufacturing even then.
As far as beliefs on slavery go, most Northerners did not think that slavery should be abolished. There were very few true abolitionists. Even Abraham Lincoln did not think slavery should be abolished. Instead, most whites in the North believed that slavery should be allowed to continue in the South but should not be allowed to spread out into the regions of the west that were not yet states.