The station is one of the earliest stations to be opened on the network, opening on 12 December 1987 when the North South line extended from Toa Payoh to Outram Park station. Cross-platform transfers between the NSL and EWL began on 4 November 1989 when the MRT network split operationally after the completion of the eastern line extension to Tanah Merah station. Due to its location at the heart of the Civic District and the numerous landmarks within its vicinity, City Hall station is one of the busiest MRT stations in Singapore.