Encyclopædia Britannica, Ninth Edition/Yankton

YANKTON, one of the principal cities of the Territory of Dakota, United States, and until recently its capital, is the county seat of Yankton county, and is situated upon both banks of the James or Dakota river at its confluence with the Missouri, and on the Chicago and St Paul and the Chicago and North Western Railroads. It serves as a centre of supply and distribution for the adjacent fertile plains. The population in 1880 was 3431; in 1888 this had probably increased to 5000.

The city derives its name from the Yankton division of the Sioux Indians. A trading-post was first established on its site in 1859, and the city was incorporated ten years later.