<P> The United States Census Bureau divides some of the northernmost United States into the Midwest Region and the Northeast Region . The Census Bureau also includes the northernmost states of the Northwestern United States, that are, within the West Region . </P> <P> Before 19th - century westward expansion, the "Northern United States" corresponded to the present day New England region . By the 1830s it corresponded to the present day Northeastern United States . </P> <P> During the American Civil War, the Northern United States was composed of the U.S. states that supported the United States of America, the Union states . In this context, "The North" is synonymous with the Union . In this context, "The South" is composed of the states that attempted secession from the U.S. to form the Confederate States of America . However, which states comprised "The North" in this context can be the subject of historical disagreement . Five slave - holding states, called the Border states, that remained with the Union--Missouri, Kentucky, West Virginia, Maryland and Delaware--may be excluded . </P>

The northern region of the united states was actually comprised of the