The Mill Creek is a stream in southwest Ohio. It flows 28.4 miles (45.7 km)[1] southwest and south from its headwaters in Liberty Township of Butler County through central Hamilton County and the heart of Cincinnati into the Ohio River just west of downtown. The section of Interstate 75 through Cincinnati is known as the Mill Creek Expressway.
The Mill Creek Valley is a remnant of the Deep Stage Ohio River from the days of the Last Glacial Maximum. The stream, with its water power and valley, were important to the development of Cincinnati. Then, for a time, the steep hillsides that surround the creek limited expansion and gave impetus to the free growth of surrounding communities that were over that barrier. Finally, inclined planes solved the problem, before highways and automobiles eliminated it.
Throughout Cincinnati's history, Mill Creek has been the scene of heavy industry. At the turn of the 20th-century, it was seen as "a great open city sewer".[2] In 1997, it was described as "the most endangered urban river in America."[3]
A USGS stream gauge on the creek at Mitchell Avenue in Cincinnati recorded a mean annual discharge of 115.9 cubic feet per second (3.28 m3/s) during the four combined water years 1942-1943 and 1946–1947.[4]
A number of substantial viaducts cross the valley of the Mill Creek. From south to north, the crossings - both high above and near the water level - are: