Early inhabitants of Yorkshire were Celts, who formed two separate tribes, the Brigantes and the Parisii. The Brigantes controlled territory which later became all of the North Riding of Yorkshire and the West Riding of Yorkshire. The tribe controlled most of Northern England and more territory than any other Celtic tribe in England. That they had the Yorkshire area as their heartland is evident in that Isurium Brigantum (now known as Aldborough) was the capital town of their civitas under Roman rule. Six of the nine Brigantian poleis described by Claudius Ptolemaeus in the Geographia fall within the historic county. The Parisii who controlled the area that would become the East Riding of Yorkshire, may have been related to the Parisii of Lutetia Parisiorum, Gaul (known today as Paris, France). Their capital was at Petuaria close to the Humber estuary. The Roman conquest of Britain began in 43 AD, however the Brigantes remained in control of their kingdom as a client state of Rome for an extended period, reigned over by the Brigantian monarchs Cartimandua and her husband Venutius. Initially, this situation suited both the Romans and the Brigantes who were known as the most militant tribe in Britain.

Queen Cartimandua left her husband Venutius for his armour bearer, Vellocatus, setting off a chain of events which changed control of the Yorkshire area. Cartimandua, due to her good relationship with the Romans, was able to keep control of the kingdom; however her former husband staged rebellions against her and her Roman allies. At the second attempt, Venutius seized the kingdom, but the Romans, under general Petillius Cerialis, conquered the Brigantes in 71 AD.

Under Roman rule, the high profile of the area continued. The fortified city of Eboracum (now known as York) was named as capital of Britannia Inferior and joint-capital of all Roman Britain. During the two years before the death of Emperor Septimus Severus, the Roman Empire was run from Eboracum by him.

Another Emperor, Constantius Chlorus, died in Yorkshire during a visit in 306 AD. This saw his son Constantine the Great proclaimed Emperor in the city, who would become renowned due to his contributions to Christianity. In the early 5th century, the Roman rule ceased with the withdrawal of the last active Roman troops. By this stage, the Empire was in heavy decline.

After the Romans left, small Celtic kingdoms arose in Yorkshire; the Kingdom of Ebrauc around York and more notably the Kingdom of Elmet in West Yorkshire. Elmet remained independent from the Northumbrian Angles until some time in the early 7th Century, when King Edwin of Northumbria expelled its last king, Certic, and annexed the region. At its greatest extent, Northumbria stretched from the Irish Sea to the North Sea and from Edinburgh down to Hallamshire in South Yorkshire.

An army of Danish Vikings, the Great Heathen Army as its enemies often referred to it, invaded Northumbrian territory in 866 AD. The Danes conquered and assumed what is now modern day York and renamed it Jórvík, making it the capital city of a new Danish kingdom under the same name. The area which this kingdom covered included most of Southern Northumbria, roughly equivalent to the borders of Yorkshire extending further West.

The Danes went on to conquer an even larger area of England which afterwards became known as the Danelaw; but whereas most of the Danelaw was still English land, albeit in submission to Viking overlords, it was in the Kingdom of Jórvík that the only truly Viking territory on mainland Britain was ever established. The Kingdom prospered, taking advantage of the vast trading network of the Viking nations, and established commercial ties with the British Isles, North-West Europe, the Mediterranean and the Middle East.

Founded by the Dane Halfdan Ragnarsson in 875, ruled for the great part by Danish kings, and populated by the families and subsequent descendants of Danish Vikings, the leadership of the kingdom nonetheless passed into Norwegian hands during its twilight years. Eric Bloodaxe, an ex-king of Norway who was the last independent Viking king of Jórvík, is a particularly noted figure in history, and his bloodthirsty approach towards leadership may have been at least partly responsible for convincing the Danish inhabitants of the region to accept English sovereignty so readily in the years that followed.

After around 100 years of its volatile existence, the Kingdom of Jorvik finally came to an end. The Kingdom of Wessex was now in its ascendant and established its dominance over the North in general, placing Yorkshire again within Northumbria, which retained a certain amount of autonomy as an almost-independent earldom rather than a separate kingdom. The Wessex Kings of England were reputed to have respected the Norse customs in Yorkshire and left law-making in the hands of the local aristocracy.

In the weeks immediately leading up to the Battle of Hastings in 1066 AD, Harold II of England was distracted by events in Yorkshire. His brother Tostig and Harold Hardrada, King of Norway, attempted a takeover in the north, having won the Battle of Fulford. The King of England marched North where the two armies met at the Battle of Stamford Bridge. Tostig and Hardrada were both killed and their army was defeated decisively. However, Harold Godwinson was forced immediately to march his army back down to the South where William the Conqueror was landing. The King was defeated at Hastings, which led to the Norman conquest of England.

The people of the North rebelled against the Normans in September 1069 AD, enlisting Sweyn II of Denmark. They tried to take back York, but the Normans burnt it before they could. What followed was the Harrying of the North ordered by William. From York to Durham, crops, domestic animals, and farming tools were scorched. Many villages between the towns were burnt and local Northerners were indiscriminately murdered. During the winter that followed, families starved to death and thousands of peasants died of cold and hunger. Orderic Vitalis put the estimation at "more than 100,000" people from the North died from hunger.

In the centuries following, many abbeys and priories were built in Yorkshire. Norman landowners were keen to increase their revenues and established new towns such as Barnsley, Doncaster, Hull, Leeds, Scarborough, Sheffield, and others. Of towns founded before the conquest, only Bridlington, Pocklington, and York continued at a prominent level. The population of Yorkshire boomed until hit by the Great Famine in the years between 1315 and 1322.

In the early 12th century, people of Yorkshire had to contend with the Battle of the Standard at Northallerton with the Scots. Representing the Kingdom of England led by Archbishop Thurstan of York, soldiers from Yorkshire defeated the more numerous Scots.

The Black Death reached Yorkshire by 1349, killing around a third of the population.

When King Richard II was overthrown in 1399, antagonism between the House of York and the House of Lancaster, both branches of the royal House of Plantagenet, began to emerge. Eventually the two houses fought for the throne of England in a series of civil wars, commonly known as the Wars of the Roses. Some of the battles took place in Yorkshire, such as those at Wakefield and Towton, the latter of which is known as the bloodiest battle ever fought on English soil. Richard III was the last Yorkist king.

Henry Tudor of the House of Lancaster, defeated and killed Richard at the Battle of Bosworth Field. He then became King Henry VII and married Elizabeth of York daughter of Yorkist Edward IV, ending the wars. The two roses of white and red, emblems of the Houses of York and Lancaster respectively, were combined to form the Tudor Rose of England. This rivalry between the royal houses of York and Lancaster has passed into popular culture as a rivalry between the counties of Yorkshire and Lancashire, particularly manifested in sport - for example the Roses Match played in County Cricket, or the Roses Tournament between the Universities of York and Lancaster.

The wool textile industry which had previously been a cottage industry centred on the old market towns moved to the West Riding where budding entrepreneurs were building mills that took advantage of water power gained by harnessing the rivers and streams flowing from the Pennines. The developing textile industry in general helped Wakefield and Halifax grow.

The English Reformation began under Henry VIII and the Dissolution of the Monasteries in 1536 led to a popular uprising known as Pilgrimage of Grace, started in Yorkshire as a protest. Some Catholics contingent in Yorkshire continued to practice their religion and those caught were executed during the reign of Elizabeth I. One such person was a York woman named Margaret Clitherow who was later canonised.

During the English Civil War, which started in 1642 between king and parliament, Yorkshire had divided loyalties; Hull famously shut the gates of the city on the king when he came to enter the city a few months before fighting began, while the North Riding of Yorkshire in particular was strongly royalist. York was the base for Royalists, and from there they captured Leeds and Wakefield only to have them recaptured a few months later. The royalists won the Battle of Adwalton Moor meaning they controlled Yorkshire (with the exception of Hull). From their base in Hull the Parliamentarians ("Roundheads") fought back, re-taking Yorkshire town by town, until they won the Battle of Marston Moor and with it control of all of the North of England.

In the 16th and 17th centuries Leeds and other wool industry centred towns continued to grow, along with Huddersfield, Hull and Sheffield, while coal mining first came into prominence in the West Riding of Yorkshire.Canals and turnpike roads were introduced in the late 18th century. In the following century the spa towns of Harrogate and Scarborough also flourished, due to people believing mineral water had curing properties.

The 19th century saw Yorkshire's continued growth, with the population growing and the Industrial Revolution continuing with prominent industries in coal, textile and steel (especially in Sheffield). However, despite the booming industry, living conditions declined in the industrial towns due to overcrowding, this saw bouts of cholera in both 1832 and 1848. Fortunately for the county, advances were made by the end of the century with the introduction of modern sewers and water supplies. Several Yorkshire railway networks were introduced as railways spread across the country to reach remote areas. County councils were created for the three ridings in 1889, but their area of control did not include the large towns, which became county boroughs, and included an increasing large part of the population.

During the Second World War, Yorkshire became an important base for RAF Bomber Command and brought the county into the cutting edge of the war. In the 1970s there were major reforms of local government throughout the United Kingdom. Some of the changes were unpopular, and controversially Yorkshire and its ridings lost status in 1974 as part of the Local Government Act 1972. The East Riding was resurrected with reduced boundaries in 1996 with the abolition of Humberside. With slightly different borders, the government office entity which currently contains most of the area of Yorkshire is the Yorkshire and the Humber region of England. This region includes a northern slice of Lincolnshire, but omits Saddleworth (now in Greater Manchester); the Forest of Bowland (Lancashire; Sedbergh and Dent (Cumbria); Upper Teesdale (County Durham) as well as Middlesbrough, and Redcar and Cleveland.

Source: http://en.wikipedia.org