Calcasieu Parish was first inhabited by the Adais of the Caddo nation of Native Americans. Later it was part of the Spanish settlements in the late 1700's then the French moved in, and later Spain again claimed the area. It became a "neutral zone" after the purchase of Louisiana by the United States, both the US and Spain claimed the territory. During this time it became a haven for outlaws and criminals because of the lack of government.

Originally a part of the much larger St Landry parish, Calcasieu was created in 1840 from the westernmost part of St Landry. It became known as "Imperial Calcasieu" because it was one of the largest parishes in the state. Later Cameron, Allen, Beauregard and Jeff Davis parishes were all carved from "Imperial Calcasieu"

The area is rich in forests and grasslands, making for cattle ranching and the development of a lumber industry. Sulfur was discovered creating a mega industry. Oil, natural gas, and gypsum are also part of the economy.