Germantown is in German Township in Montgomery County, north of Butler County. A city web site says: "The Twin Valley was a 'valley of peace' for the various Indian tribes hunting here. The Shawnees had a settlement nearby as late as 1804. The first pioneers arrived in the area in 1798 and stayed about six years before most moved on. Germantown was settled in August 1804 by German-speaking families from Pennsylvania. They were led by Philip Gunckel, the only original settler who spoke English. He selected the Twin Valley as a site for a grist mill." Gunckel and others arrived from Berks County in Pennsylvania. The German language was spoken in Germantown until the early 1900s. Gunckel established the first plat in 1814. The village incorporated May 16, 1833, and the population had grown to 1,200 by 1840." A post office was established in 1818 with Peter Schaeffer as first the postmaster.
According to the city web site, "in May 1976, the downtown core, known as the 'Gunckel Town Plat'" was recognized by the National Historical Park Service of the U.S. Department of the Interior as a National Historic Site and Historical Preservation District. Also attaining national recognition were the Shuey Mill, the Poast House, and the Watson (Rohrer) House." The Germantown and Dayton Pike was completed in 1837. The first successful railroad, the Cincinnati and Northern, was built through the town in 1869. Germantown became a city in 1980. The 1882 Montgomery County history says: "Germantown is situated in the Twin Valley with Little Twin Creek on its east side and Big Twin on its west and south sides, being in the forks of these streams. It was laid out by Philip Guncke, who, Oct. 4, 1814, "certified that the plat as recorded was correct. The first sale of lots occurred Oct. 21, 1814, and the second sale Nov. 10, 1815."
"It was called Germantown," said the 1882 history, "because the people who built up the town and lived around it were Germans. Howe, in his Historical Collections of Ohio, says 'Germantown was named from Germantown. Pa.,' but in this he is mistaken; the name was given for the reason just stated." (See Montgomery County, German Township and Sunbury.)