海城県の県城から西へ離れた牛荘鎮はかつては遼河の河口に位置したため、遼代以来満州の海の玄関として栄えており、清代中頃にはその繁栄は頂点に達した。1858年に清が結んだ天津条約で牛荘は条約港となったが、土砂の堆積で大きな船が入れず、1864年により河口に近い営口に新港が建設されて条約港が移り、以後衰退していった。日本は営口に置いた領事館を「牛荘領事館」と呼称している。

Yingkou was historically known as Newchwang (Chinese: 牛庄; pinyin: Niuzhuang; Manchu: Ishangga gašan hoton) in postal romanization; it was one of the Treaty Ports opened under the Treaties of Tianjin of 1858. In fact, the actual town of Newchwang was about thirty miles upstream of Liao He, within today's county-level city of Haicheng. After the treaty had been signed, the British found that the river near Newchwang was too shallow for their ships. Instead, the treaty port was moved to the area nearer to the river mouth where today's Yingkou is located.

To avoid confusion between the two locations, careful English writers of the early 20th century would sometimes use Newchwang for Yingkou (explaining that "Ying-kow, ... outside Manchuria, ... is known only as Newchwang") and Niu-chuang (the proper Wade–Giles transcription of '牛庄') for the actual inland Niuzhuang Town.[2] Meanwhile, Newchwangcheng (牛庄城; postal:Newchwang Town) was adopted by the government as the inland town's name to distinguish it from the coastal city.