Oneco is located in Oneco Township about one mile south of the Wisconsin-Illinois state line, about one mile from the Richland Creek and the path of the railroad.

The stagecoach road from Chicago to Prairie du Chien by way of Rockford and Mineral Point passed through Oneco Township, and its angling course decided the direction still maintained by Oneco’s one street. The other pioneer road crossing the township connected Freeport with Monroe, Wisconsin. Oneco marked the intersection of the two roads. Its mill was a mile away beside the creek and was run in the 1840s by C.W. Brown. John LaBorde built a new mill and was the miller for about 30 years, closing the operation in the 1890s.

In the early 1850s, Oneco and Orangeville were contenders for growth. However, by the early 1880s, Orangeville had won the contest easily, partially because of the placement of the mills in the two villages. Therefore, when the ICRR built the rail line between Freeport and Monroe, the rail line did not pass through Oneco.