Upper Saxony
It was particularly to distinguish the lands from 'Lower Saxony', a concept which arose later in popular usage (though never enforced) as a term for the original Saxon lands in north and west Germany (where Low German dialects had spread), in what is now the state of Lower Saxony, as well as the adjacent Westphalian region, Holstein and the western part of today's Saxony-Anhalt north of the Harz range (Eastphalia).
History of Saxony-Anhalt
In 1813 the Kingdom of Prussia occupied large amounts of Saxony's territory in the Battle of Leipzig, including the Electoral Circle (which had been renamed the "Wittenberg Circle" in 1807); in May 1815 a treaty was signed in which Saxony ceded this territory to Prussia. In June 1815 they all became part of the German Confederation. In 1816 Prussia reorganised its annexed territory, merging it with the former Duchy of Magdeburg, Principality of Halberstadt, Principality of Erfurt, the Eichsfeld, and the former Imperial Cities of Mühlhausen and Nordhausen, along with the Altmark and other parts of Brandenburg west of the Elbe, into the Province of Saxony.