Byrnes Mill is a city in northern Jefferson County, Missouri, United States. The population was 3,173 at the 2020 census.
History
The settlement was founded by Patrick C. Byrnes, who immigrated from Ireland in 1849. His family established a mill on their property. A descendant sold the mill and most of the property in 2008.
Geography
According to the United States Census Bureau, the city has a total area of , of which is land and is water.
The city is located on the Big River, and has the ruins of an old mill and dam.