Hello Herga Kitty and Santa
Middlesbrough is correct .
Many moons ago +/- 100 Years when the were receiveing the Towns Charter or whatever the process was , the Town Clerk actually misspelt the Towns intended name - the intention was, it should be the same as all the other English towns as a Borough - Scarborough , Peterborough,Guisborough etc.so we're stuck with it !!!!
Imagine dropping a bollock of such magnitude and still keeping your job !!!