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is a census-designated place (CDP) in Jefferson County, Missouri, United States. The population was 4,373 at the 2000 census. It was originally known as West Kimmswick, and is roughly 25 driving minutes south of St. Louis. St. John's Church is a historic parish church located within Imperial.
According to the United States Census Bureau, the CDP has a total area of 6.1 square miles (15.9 km²), of which, 5.4 square miles (13.9 km²) of it is land and 0.7 square miles (1.9 km²) of it is water. The total area is 12.09 water.
Imperial is located near Arnold, directly to the north, and near Barnhart, to the south. I-55 Highway runs through Imperial. Imperial Main Street runs through Imperial near Kimmswick. Mastodon State Historic Site is located in Imperial on West Outer Road and on Seckman Road.