Slavery was in all the 13 Colonies until its abolishment after America's independence. Slavery in New England grew even after America became a country. New Jersey held slaves until the 1850's. During the Civil War at Fort Jefferson in Florida, the Union army supplied slaves for to maintain the fort. Slavery fell in the North because industry grew. Many of the former slaves became sharecroppers or were sold in a slave state. Today in the North (where I live) I don't see a difference to the racism then the South. It's just America!
The South is widely accepted to be the "more racist" area of the country, but the Northern states have had their fair share of issues. The fact of the matter is that, although the Northern states didn't have the same structure of slavery and sharecropping that the Southern states did, the North was just as divided.
OPEN racism was epidemic and has always been epidemic everywhere in America. There was NO CLOSET RACISM in America. White (old stock) Americans were openly a violently racist. Many lynched Italians, Spaniards, blacks. They were openly racist. There was no difference in region. AT ALL. America was an OPENLY racist country regardless of where you went. People are dumb.
In idealistic terms, racism anywhere is an issue. Racism, sure, existed in the north and was, therefore, a problem. Yet, I think that the word "problem" implies a wide-spread, chronic, or crisis-inducing situation. In the North, this was only very rarely the case (i.E. Only like the KKK rallies in Ohio).
I think it's maybe a little more accurate historiologically to discuss it as a phenomenon in the North, rather than a "PROBLEM" per se.