In the 1st century BCE there was an Iron Age fort on the site, but more continuity started when King Ceolred of Mercia built a wooden fortress there. The place was attacked by King Ine of Wessex in 716 in a battle so bloody that the location was called Slain Hollow (until Pugin turned it into an oriental water garden).
After the Conquest of 1066, the castle was rebuilt and enlarged in stone by the Norman noble Bertram de Verdun, who had been granted land in England by William. It stayed in the Verdun family through three generations of "Bertram de Verdun"s; then, in 1318, Joan de Verdun married Thomas de Furnival. Thomas died crusading in 1348, and the estate went to Sir John Talbot who married Furnival's daughter Maud. Talbot was created the first Earl of Shrewsbury (sort of; I'll explain later). Alton Castle stayed in the Talbot family; the 16th Earl of Shrewsbury was the owner during the 19th century expansion, after which the building was renamed Alton Towers.
In the 20th century the grounds were opened to the public, and now in the UK the phrase "Alton Towers" invokes images of an enormous theme park and resort that has been developed at the site.
But back to the first Earl of Shrewsbury. The first Earl of Shrewsbury was not the first; I'll explain how there were two "firsts" tomorrow.