New Philadelphia is the county seat of Tuscarawas County.. It is located 71 miles south of Cleveland on the Tuscarawas River. It was first incorporated in 1808. Coal and clay are found in the vicinity. In the past, mining interests and the manufacturing of steel, canned goods, roofing tile, sewer pipe, bricks, vacuum cleaners, stovepipes, carriages, flour, brooms, and pressed, stamped, and enameled goods occupied the people. In 1900, 6,213 people lived here; in 1910 8,542; in 1920, 10,718; and in 1940, 12,328 people lived here. The population was 17,288 at the 2010 census.
New Philadelphia is adjacent to the city of Dover, which is almost the same size. The two cities are considered to be twin cities.
The Moravian Church founded Schoenbrunn ("beautiful spring") in 1772 as a mission to the Delaware Indians. The settlement grew to include sixty dwellings and more than 300 inhabitants who drew up Ohio's first civil code and built its first Christian church and schoolhouse. Problems associated with the American Revolution prompted Schoenbrunn's closing in 1777.
The founder, John Knisely, returned to Ohio in 1804 with his family and 33 other pioneers, he also hired surveyor John Wells to plot out New Philadelphia in the same grid style as Philadelphia, Pennsylvania.