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is a city in Jefferson County, Missouri, United States. The population was 4,247 at the 2000 census.
Crystal City and its neighbor Festus are often collectively known as the "Twin Cities"; however, they are incorporated separately.
According to the United States Census Bureau, the city has a total area of 3.7 square miles (9.7 km²), of which, 3.7 square miles (9.7 km²) of it is land and 0.27% is water.