Yes, it was. There were other points of difference between the North and South, but they all went back to slavery one way or another. For instance, the Southern landowners opposed the Whig program of protective tariffs on manufactured goods, which protected/stimulated Northern industry while doing nothing for Southern agriculture but raising the price of manufactured goods farmers needed. But why was it, that the North was industrialized and industrializing while the South was almost purely agrarian? Partly, no doubt, because of the difference in climate – pre-air-conditioning, heat and humidity make everyone and everything slower – and partly because the North was better endowed with coal veins and waterheads. But also because the South was dominated economically, politically, socially and culturally by a landowning/slaveowning elite which consciously equated itself with the feudal lords of medieval Europe, had a lot of emotional investment in an 18th Century mode of society and economy, and was hostile to the very idea of industrialization. This, together with the relative inefficiency of slave labor for industrial production, and the lack of a mobile free labor force for the purpose, tended to freeze out industrialization.
Yes it is, in terms of slavery’s political/social/economic consequences: After the Civil War, the Southern Bourbon aristocracy (so called because, like the French Bourbons after the Revolution and Napoleon, they “learned nothing and forgot nothing”), still maintaining their local hegemony, and wanted something as near to their antebellum way of life as possible under the circumstances, became in effect regional managers for the Northeastern elite, running the whole South as an agrarian-and-extractive economy, based on the undercompensated labor of blacks and, to lesser degree, poor whites. Much like the slave days, but without the job security. This, again, froze out industrialization, despite repeated attempts to declare a "New South. And the Jim Crow system, unmistakeably a legacy of slavery, was all bound up with maintaining that whole set of cultural assumptions.
It is no coincidence that the Sunbelt economic revolution did not really take off until after the Civil Rights revolution. Certainly New Deal electrification and post-WWII availability of air conditioning helped, but Jim Crow was without a doubt holding back economic development in the South and keeping it a Gothic backwater. White Southerners should consider Martin Luther King, Jr., a greater Southern hero than Thomas Jefferson, Jefferson Davis or Robert E. Lee; he did more of real value for the South, including the white South, than any of them.