In the second half of the 20th century the port was considerably expanded beyond its locked dock, and east and west jetties; with the addition of several deep water jetties for bulk cargos: this included the Immingham Oil Terminal (1969, expanded 1994) for oil importation to the new Continental Oil and Lindsay Oil refineries; the Immingham Bulk Terminal (1970) built as a joint scheme by the National Coal Board and British Steel Corporation for coal export and iron ore import; the Immingham Gas Jetty (1985) for LPG import; and the Humber International Terminal (2000, expanded 2006) for bulk cargos.

From the mid 19th century onwards the Manchester, Sheffield & Lincolnshire Railway developed the Port of Grimsby into a modern outlet for its rail system onto the east coast of England.

[6] The Great Central Railway (GCR), owner of the Grimsby Docks was willing to back the scheme, but sought the advice of Sir John Wolfe Barry, who reported that the approach channel to the dock would have required extensive dredging; he later reported in favour of a scheme near Immingham, similar in location to that earlier proposed by Liddel.

[9] Under pressure from interested parties the Board of Trade commissioned an inspection of the channels, which reported that no serious negative change would be expected from the new dock works.

Features of the scheme were: a new dock in the parish of Immingham with lock and entrance channel, with jetties on the east and west side; a railway with a junction north of the Great Central Railway's line at Ulceby station to the dock; and rights to dredge, divert streams (Immingham Haven), to raise funds, to make working arrangements with the Great Central Railway; and rights of compulsory purchase.

5. c. xx), which extended the time for construction, allowed raising additional capital, and made minor changes to the original plans.

[15] The dock was designed by the firm of Sir John Wolfe Barry and partners, and contracted to Price, Wills and Reeves (Westminster), constructed on a site of over 1,000 acres (400 ha), with a river frontage of about 1.5 miles (2.4 km).

[16][18] The light railway to Grimsby was connected to the Great Coates branch by 1906; the line was used during the construction of the dock by the contractors, and a passenger service was begun in 1910.

[19] Initial work on the dock included diversion of drains, and dredging of the entrance channel to the Humber.

[32] For both purposes a power station, 188.5 by 104.5 feet (57.5 by 31.9 m) in ground plan was erected on the dock estate west of the main lock entrance.

The silo was built by Stuart's Granolithic Company, and grain handling equipment supplied by Henry Simon (Manchester).

[46][47] During the war John Dowland and Leonard Harrison received the George Cross for defusing a bomb that had fallen onto the grain ship SS Kildare in February 1940 in Immingham Dock.

[45] The Immingham Oil Terminal (IOT) jetty on the banks of the Humber east of the dock entrance was opened 1969.

[50] Immingham Bulk Terminal was commissioned in 1970 jointly by the National Coal Board (NCB) and British Steel Corporation (BSC) in association with the British Transport Docks Board (BTDB) for the export of coal and import of steel.

[map 18][63] In 2005 Associated British Ports decided to invest a further £15 million on a "Phase 2" extension of the terminal.

[64] The phase two berth extended the terminal's quay by 220 metres (720 ft), and was built primarily to handle imported coal.

[65] A new Immingham West Jetty for petrochemical handling was contracted to Edmund Nuttall to a design by engineering firm Halcrow.

[66] In 2004 transport minister David Jamieson allowed the construction of a £35 million, 5 berth roll-on/roll-off terminals at the port, for ferry operators DFDS Tor Line, suitable for vessels up to 225 by 35 metres (738 by 115 ft).

[67][68] The Immingham Outer Harbour Revision Order, 2004 permitted the construction of moorings and access ramps south and west of the jetty of the Humber International Terminal; and the removal of part of the Western jetty; as well as permitting dredging of a channel to the terminal to a maximum depth of 9 to 10 metres (30 to 33 ft).

[49][71][map 19] In 2007/8, a £45 million 200,000 ton (227,000 cubic metres (8,000,000 cu ft)) pa biofuel plant was constructed at the Port of Immingham, manufacturing biodiesel from vegetable oils.

[72][73] In 2008 a 48 acres (19 ha) site was acquired in Stallingborough in 2008 to increase off dock estate storage space for cars.

ABP's total investment in biomass handling facilities, including installations at Hull and Goole was to be around £100 million.

[74][note 2] In April 2013 Graham Construction was awarded the contract to build the 3 million ton per annum facility, consisting of an automated biomass handling terminal utilizing continuous ship unloaders, with rail and road export facilities, and with 100,000 ton storage capacity, using four silos each of 168,000 cubic metres (5,900,000 cu ft).