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
After 1918 Saxony was a state in the Weimar Republic and was the scene of Gustav Stresemann's overthrow of the KPD/SPD led government in 1923. It continued to exist during the Nazi era and under Soviet occupation. It was dissolved in 1952, and divided into three smaller 'Bezirke' based on Leipzig, Dresden and Karl-Marx-Stadt, but reestablished within slightly altered borders in 1990 upon German reunification. Today the Free State of Saxony also includes a small part of former prussian Silesia around the town of Görlitz which remained German after the war and which for obvious reasons of unviability as a separate state was incorporated into Saxony. This part had been part of Silesia only after 1815 and belonged as part of Upper Lusatia to Bohemia before 1623 and previously to Saxony between 1623 and 1815.