Troy City (1990 pop. 19,478), seat of Miami co., W central Ohio, on the Great Miami River, in a farm area; inc. 1814. Welding machinery, food-processing equipment, motor generators, paper products, and tools are manufactured. Growth and industrialization came with the arrival of the Miami and Erie Canal in 1837. A disastrous flood in 1913 resulted in the creation of the first flood protection district in the United States.