The Carlisle class ships were ordered in July 1917. They were to be similar to the Ceres class but with improved bows (increased in height by 5') to decrease the amount of water coming over them.
The Carlisle originally had a hanger under the bridge but it was removed in 1920.
The Cairo and Calcutta were converted into anti-aircraft cruisers in 1938 / 1938 - 1938. Capetown was scheduled to be converted but the start of World War II changed that.