Straddling the border between County Durham and North Yorkshire, it spans the boroughs of Middlesbrough, Stockton-on-Tees and Redcar and Cleveland.

Before the county of Cleveland was created, the area (including Stockton-on-Tees) existed as a part of the North Riding of Yorkshire, due to most land being south of the Tees.

[3] Compared to the modern Teesside conurbation, the area was smaller, then excluding towns such as Hartlepool, Ingleby Barwick and Yarm, the latter two being in the Stokesley Rural District until Cleveland was created.

This name and area carried over to an enterprise partnership formed in 2011 and a combined authority created in 2016, twenty years after the abolition of the Cleveland county.

Today Venator Materials is based close to Greatham, operating one of the world's largest chemical plants for titanium dioxide manufacturing.

In 1860 William James established an alkali company at Cargo Fleet and in 1869 Samuel Sadler also set up a factory nearby.

[10] The chemical industry was established at Billingham in 1918 by the Government for the production of synthetic ammonia, with its intended use being the manufacture of munitions during the Great War.

Teesside's first chemical works was when Robert Wilson produced sulphuric acid and fertilisers at Urlay Nook near Egglescliffe in 1833.

Another chemical plant was established the following year to make oil and petrol from creosote and coal by a process called hydrogenation.

The ore was discovered by geologist John Marley and first used by John Vaughan, the principal ironmaster of Middlesbrough who along with his German business partner Henry Bolckow had already established a small iron foundry and rolling mill using iron stone from Durham and the Yorkshire coast, with the new discovery prompting them to build Teesside's first blast furnace in 1851.

[15] Many more iron works followed, such as those built in the region by Losh, Wilson and Bell (see Sir Issac Lowthian Bell) who in 1853 were operating 5 furnaces in the region.The success of John Vaughan and Henry Bolckow's first blast furnace meant that by 1873 Middlesbrough was producing 2 million tonnes of pig iron a year.

More and more blast furnaces were opened in the vicinity of Middlesbrough to meet this demand such that by the end of the century Teesside was producing about a third of the nation's iron output.

it has crept out of the Cleveland Hills where it has slept since Roman days, and now like a strong and invincible serpent, coils itself around the world"[17] By 1929 the great depression began to effect Britain and the famous name of Bolckow-Vaughan merged with neighbour Dorman-Long & Co. who then became Britain's biggest iron and steel maker and employed 33,000 people.

In 1954 the post-war boom saw Dorman-Long build a state of the art steelworks at Lackenby and then new blast furnaces at Clay Lane.

1967 saw Dorman-Long become part of the nationalized British Steel Corporation as production boomed in Britain and in 1979 the largest blast furnace in Europe was erected at BSC's new Redcar plant.

The history of Teesside and its rapid growth during the 19th century is directly linked to the expansion of the railways from Darlington and Stockton towards the mouth of the Tees estuary and the subsequent discovery of ironstone in the Cleveland Hills which attracted iron companies to the area.

[19] Teesside continues to be used locally to refer to the entire urban area and the name can still be seen in the following uses: It has also been adopted for various other purposes as a synonym for the former county of Cleveland.