New River and Old River were names which appeared after a change in the course of the Great Miami River in March 1805. Stephen Cone explained it this way:
"In the years 1803-04 James Smith and Arthur St. Clair, son of General St. Clair, erected a mill at a bend of Four Mile Creek, about a mile and a half above its mouth, and dug a race from the Miami River to bring the water to their mills, in order to supply an additional quantity when the supply from the creek failed. In the month of March 1805, an extraordinary flood occurred in the Miami River, which tore away the headgates of their race, forcing a channel through the same, and thence along the bed of Four Mile Creek. This flood entirely destroyed their mill property and carried away the works, and from that time the channel thus formed continued to widen and deepen until, in a few years, at ordinary stages of the river, the whole of the new water passed through it and it acquired the name of New River. The island formed between the new and old channels contained about 350 acres, and was known as Millikin's Island, now known as Campbell's Island. The reservoir of the Hamilton Hydraulic is formed by using the bed of Old River." Mrs. Heiser said the river change was beneficial to Hamilton. "It may be said that this disaster started Hamilton on her fine industrial career. The river, in changing its course, left the channels of the hydraulic works, which later furnished power for a great manufacturing center."