He made a success of the business through several innovations, notably replacing the wooden upper decks with iron ones which increased the strength of the ships; and giving the hulls a flatter bottom and squarer section, which increased their capacity.
Harland subsequently made Wolff, his assistant, a partner in the company. Wolff was the nephew of Gustavus Schwabe, a financier from Hamburg. Schwabe had heavily invested in the Bibby Line, and the first three ships that the newly incorporated shipyard built were for the that line.
When Harland died in 1894, William James Pirrie became the chairman of the company until his death in 1924. It was during this period that the company built the RMS Titanic and her sister-ships RMS Olympic and HMHS Britannic between 1909 and 1914. These were three of over 70 ships constructed for the White Star Line.
In 1912, the company acquired another shipyard at Govan.
During the First World War, Harland and Wolff build monitors and cruisers, including the 18-inch gun armed "large light cruiser" HMS Glorious.
In 1918, the company opened a new shipyard on the Eastern side of the Musgrave Channel which was named the East Yard. This yard specialised in mass-produced ships of standard design developed during the first World War.
The company started an aircraft manufacturing subsidary with Short Brothers, called Short and Harland Limited in 1936. Its first order was for 189 Handley Page Hereford bombers built under license from Handley Page for the Royal Air Force. During the Second World War, this factory built Shorts Stirling bombers as the Hereford was removed from service.
The shipyard was very busy during the Second World War, building 6 aircraft carriers, 2 cruisers and 131 other naval ships; and repaired over 22,000 vessels. It also manufactured tanks and artillery components. It was during this period that the company's workforce peaked at around 35,000 people. The yard on Queen's Island was heavily bombed by the Luftwaffe in April and May 1941 causing considerable damage to the shipbuilding facilities and destroying the aircraft factory.
With the rise of the jet powered airliner in the late 1950s, the demand for passenger ships declined; and this coupled with competition from Japan led to difficulties for the British shipbuilding industry. The last cruise liner that the company built was the RMS Canberra in 1960.
In the mid-1960s the British Government started advancing loans and subsidies to British shipyards to preserve jobs. Some of this money was used to finance the modernisation of the yard, allowing it to build the much larger post-war merchant ships including one of 333,000 tonnes. However continuing problems led to the company's nationalisation in 1975.
The company was bought from the British government in 1989 in a management/employee buy-out in partnership with the Norwegian shipping magnate Fred Olsen; leading to a new company called Harland and Wolff Holdings Plc. By this time, the number of people employed by the company had fallen to around 3000.
For the next few years, Harland and Wolff specialised in building standard Suezmax oil tankers, and has continued to concentrate on vessels for the offshore oil and gas industry. It has made some forays outside of this market - for example unsuccessfully bidding against Chantiers de L'Atlantique for the construction of Cunard's new Queen Mary II, and recently completing two roll-on roll-off ships.