To distinguish the context between the county and the city.
To say that 'small farms are found everywhere in Durham' might surprise some people. 'Small farms are found everywhere in County Durham' would be more re-assuring!
Nope, the word 'county' was in use here for centuries before anyone from England decided to settle in America.
The Anglo-saxon word was 'shire'. After the Norman French took over in the 12th century, the word 'county' became applied to the shires, since each was ruled over by a Count.
Both words are still in use today, as in 'the County of Hampshire'.
It is a Palatinate. It was ruled over by the Prince Bishop. The Bishop of Durham. Set up as a bulwark against the marauding Scots.
It was such a wild country that William the Conquerer (or William the ******* as he was known) did not include it in the Domesday Book. He just left it all to the Bishop who is 3rd in seniority in the Church of England.
The Shires were a much more peaceful and law abiding.
A Palatinate was ruled over by (usually) a Bishop. They were on the Marches or borders. ie Durham & Lancaster bordered Scotland & Cheshire bordered Wales. The Idea being that the Bishops would keep out the marauders and save the King the bother.
I reckon Durham just hung onto the title as we are a bit old fashioned here.
For about 11 years the River Tees was the border between England & Scotland. Can't remember the dates off hand.