Steam Incorporated, often abbreviated to Steam Inc., is a railway heritage and preservation society based at the Paekakariki Railway Station, Paekakariki at the southern end of the Kapiti Coast, approximately 50 minutes north of Wellington on the west coast of New Zealand's North Island. Unlike some societies who operate on preserved sections of closed branch lines (e.g. the Kingston Flyer on the Kingston Branch or the Pleasant Point Museum and Railway on the Fairlie Branch), Steam Incorporated own a depot ("The Engine Shed") beside one of the country's most important railway lines, the North Island Main Trunk Railway, and restores heritage locomotives and for use on excursions on the regular national rail network.
Paekakariki's close association with the railway began in 1886 when the Wellington and Manawatu Railway Company's line from Wellington to Longburn opened. Paekakariki Railway Station was a large station despite the settlement's small size, as it was ideally located as a locomotive changeover point - powerful engines were required to tackle the difficult grades between Wellington and Paekakariki, while lighter and more nimble ones were better suited to the gentle grades and straight track through the Kapiti Coast and Horowhenua to Manawatu. The New Zealand Railways Department (NZR) took over the Wellington and Manawatu Railway in December 1908, but Paekakariki's status as an important depot remained unchanged. In 1940, the line from Wellington to Paekakariki was electrified and Paekakariki's depot was altered: it became the changeover point from electric to steam motive power, or electric to diesel from the 1950s onwards. Paekakariki also was an important goods transfer point between the Railways and its "Rail Air" service that operated out of Paraparaumu across Cook Strait, before the Rail ferries. A large goods shed was constructed at Paekakariki by U.S. Marines stationed in the area for use with the Rail Air service during World War II. In the late 1960s with steam power coming to an end, the locomotive depot in Paekakariki was closed and the diesel locomotives which replaced steam were based out of Wellington instead. The main engine shed was demolished along with a number of other buildings, but the Rail Air Shed, two signal boxes, amenities building and a turntable remained when Steam Incorporated acquired the site. New sheds were constructed to replace those demolished, and the Rail Air Shed & amenities buildings were acquired when it became available. While initially leasing a portion of the site, Steam Incorporated now owns the whole former depot site including the 70ft turntable however the railways retain a right of access to the turntable.