Folkestone Harbour opened in 1848 and was electrified in June 1961.
The opening of the Channel Tunnel in 1994 led to most of the ferry operators leaving Folkestone. However Hoverspeed continued to serve the port with its SeaCat service to Boulogne. This meant two train services a day continued to operate to the station until September 2000, when Hoverspeed moved to Ramsgate. Rail services to the Harbour station ceased from the Summer 2001 railway timetable and not long after the live rail was de-energised. The lack of maintaince meant the removal of the 'Up' line in 2002.
There have been several 'official closures' since 2001. There was a closure ceremony on 12 April 2008, and an 'official' last train. However, objections to the closure were made by English, Welsh and Scottish Railway (now DB Schenker), The Department for Transport and Southeastern. The latter being responsible for train services in the area.
Until 2009 there were still trains to the Harbour station in the form of the twice weekly V.S.O.E. The train would run from London Victoria to the harbour station where passengers were transferred onto a coach for the journey to the Eurotunnel terminal where a Shuttle would take them to Calais from where they could rejoin the V.S.O.E in France.
The formal closure process for the line started on March 20th 2009.
However, since then one train a year (not in passenger service though sadly!) has passed along the line, suggesting it is not yet dead completely!