Early European settlement in New Zealand was small, with only around 200 settlers by 1840, but increased rapidly after the Treaty of Waitangi established British sovereignty over New Zealand in 1840. The gold rushes of the 1860s attracted immigrants from outside Britain, particularly Americans and Chinese. The largest wave of immigration came in the 1870s, when over 289,000 people arrived in New Zealand over 15 years. Later waves saw immigrants from the Pacific Islands in the mid-20th century for work, and from Asia starting in the late 1990s, particularly from China, Hong Kong and Korea.