Who is the narrator, can she or he read minds, and, more importantly, can we trust her or him?
Third-Person Omniscient
At first it might seem like the narrator of this book is third-person omniscient, since it sticks pretty closely to Margaret Hale's point of view. But as the story gets going, the narrator seems to get more and more comfortable with bouncing around between different characters and perspectives. One of the first major breaks from Margaret's point of view occurs in Volume 1, Chapter 9, which tells us "[in] Mr. Thornton's house, at this very same time, a similar, yet different, scene was going on" (1.9.16). This sudden flash to a completely different house shows us that the narrator is totally capable of moving around.
One weird aspect about the point of view in North and South is that there are parts of this book where the narrator uses the word "I." This ain't third-person omniscient at all. But these incidents are so rare that you're better off calling this book third-person omniscient. One of these "I" cases happens at the end of Volume 2, Chapter 4, where the narrator says, "But [Mr. Thornton] was no great analyser of his own motives, and was mistaken, as I have said" (2.4.27).
What's going on? Well, you well know, North and South is a big fattie of a book. And when it was first published the editor was probably not able to catch all of the glitches: there was no "find and replace" in the Victorian publishing industry.
While these rogue "I's" might make you want to label this book's point of view as first-person, don't. Overall, it leans way more toward third-person omniscient.