The first king considered to have ruled over the whole of England was Æthelstan (also spelled Athelstan). He reigned from 924 to 939 AD. Æthelstan was the grandson of Alfred the Great and the son of Edward the Elder. After initially becoming king of Mercia, then Wessex, he effectively united these territories and conquered the Viking kingdom of York by 927, establishing himself as the first king to rule over a unified England. He was crowned at Kingston upon Thames on September 4, 925, and is noted as the first English king to wear a crown rather than a helmet during his coronation. His rule marked the beginning of what is recognized as the Kingdom of England.