From the Wikipedia page 
South Dock railway station was a station in the Isle of Dogs, east London. It was between Millwall Junction railway station and Millwall Docks railway station on the Millwall Extension Railway (MER) branch of the London and Blackwall Railway which opened to goods traffic on 18 December 1871 and to passengers on 29 July 1872. The station was on the northern side of the South Dock of the West India Docks, near the eastern end. The station had an island platform as was the only passing loop on the branch.
Passenger traffic at the station was always light and passenger service to it, and the rest of the MER extension, ceased in 1926, though goods services continued until the docks closed in the 1970s. Extensive rebuilding in the 1980s Docklands redevelopment has left no trace of the station or the line