The next meeting was on December 8, 1840. It was resolved at this meeting that the seat of justice be given the name of Marion. In 1843, the Legislature authorized the people to vote on the question of moving the parish seat, but apparently no change was made at that time. In 1852, however, Jacob Ryan secured the removal of the seat of justice from Marion to the east bank of Lake Charles. This parish seat was incorporated as a town in 1857 as Charleston and was reincorporated in 1868 as Lake Charles. It is located about six miles from the original parish seat of Marion, which is now known as Old Town. The name, Lake Charles, perpetuates the memory of one of the first settlers, Charles Sallier, an Italian who took up land in this area at the beginning of the 19th century.
The parish boundary was reduced in 1870 when Cameron Parish was cut off from the south portion of Calcasieu. These limits remained until 1912, at which time it comprised an area of over 3,600 square miles and was the largest parish in the state, and for this reason is sometimes called "Imperial Calcasieu." In 1912, the three parishes of Allen, Beauregard, and Jefferson Davis, with a total area of approximately 2,548 square miles, were cut off from the Parish of Calcasieu. These were the last parishes created in Louisiana.
It is interesting to note that the river from which the parish derives its name is shown on some older maps as "Bayou Quelqueshue" and sometimes as Calcasieu. Calcasieu, which means "crying eagle" in English, is said to have been the name of an Attakapas Indian chief who gave a peculiar cry like an eagle as he went into battle.