Why are there so many Northeasters in Henan?

This is mainly due to the historical population movement, and many Henan people immigrated to the northeast to settle down. The main wave of immigration was after the founding of the People's Republic of China.

It is precisely because of the war at the end of the Ming Dynasty that General Longhu of the Ming Dynasty rebelled with Jian, Tongzhi and Governor Nurhachi, constantly invading Liaodong, burning and looting, killing or enslaving Han people, causing a large number of Han people to flee or die, and the population dropped seriously. There was a brief opening in the early years of the Qing Dynasty, but it was quickly banned in the northeast, because the first Manchu emperor after entering the customs was the emperor shunzhi. At that time, the Central Plains was in turmoil, and there were still remnants of the Ming Dynasty in the south trying to restore the country. In the case that the Manchu regime in Beijing may be overthrown, the Manchu needs to hold Manchuria, the base area where they can retreat. In addition, Manchu people think that Northeast China is the land of Longxing, which has geomantic value and military strategic significance. Therefore, in the Ming Dynasty, the emperor shunzhi ordered the construction of a "wicker edge" along the Liaodong side wall to separate the Northeast from the Central Plains. The wicker border starts from Fengcheng in Liaoning in the east and ends at Shanhaiguan in the west. Trenches are dug, piles of soil are dikes, wickers are inserted on the dikes, fences are built, and soldiers are stationed. People in Shanhaiguan can only go out with printed tickets issued by the government, and they don't issue them when they have nothing to do. During the prosperous period of Kanggan, the Manchu regime was stable, but in order to preserve Manchu customs in Northeast China and prevent Manchu from being sinicized, Han people were still prohibited from entering Northeast China. In the seventh year of Kangxi (1668), the national ban policy was implemented, resulting in a large number of no-man's land in Northeast China. Emperor Qianlong once issued an imperial edict, clearly stipulating that farming and logging were prohibited in the land in Northeast China, and a large area of wilderness was reserved to maintain the custom of riding and shooting with the Eight Banners. Since the promulgation of the law, Northeast China has been formally incorporated into the national legal system, and the Qing government has intensified the investigation of people who go through customs, searching for Han people who secretly go through customs in Northeast China, and sent them back to their places of origin as soon as they are found.