For me, it is Heilongjiang, Jilin, and Liangning. These three provinces actually used to be six provinces under the Kuomingtang before 1949. Parts of the land there were lost due to invasions by Russia as well as the independence of the Republic of Mongolia. The ethnic Han in Dongbei actually have a very short history of living there. The Manchurians did not lift the ban on Hans immigrating there until the early 1890's. Granted there were Han who still did labor as well as specialized jobs but there were few. Most of the Chinese who live there now can trace their ancestry back to Shandong province. There was a massive wave of immigration from Shandong to Dongbei in the early 20th century. The Han who lived in Dongbei during the Ming Dynasty were killed off via Genocide by the Manchurians.

Even to other chinese dongbei folks are not viewed favorably. From what I have seen and heard both from talking with Chinese folks as well as reading their discussion boards they will view folks who are from there as being ill tempered, prone to alcoholism(even for China!), unwilling to be reasonable, and flat out bullying. I myself find folks from this area to be less willing to think for themselves and more willing to live life with the mantra of "follow the biggest bully on the block". Their mentality is slavish even for China. Be very, very careful when you're dealing with folks from this area.