In 1903, it officially changed its name to the Grand Duchy of Saxony (German: Großherzogtum Sachsen), but this name was rarely used.

The Grand Duchy of Saxe-Weimar-Eisenach consisted of three greater areas, each of which formed a Kreis administratively, plus several exclaves.

Neighboring countries were Prussia, Saxony, Bavaria, Hesse-Kassel (until 1866, when it was incorporated in the Prussian Province of Hesse-Nassau), and all the other Thuringian states (Saxe-Altenburg, Saxe-Coburg-Gotha, Saxe-Meiningen, Reuss Elder Line, Reuss Junior Line, Schwarzburg-Rudolstadt and Schwarzburg-Sondershausen).

The duchies of Saxe-Weimar and Saxe-Eisenach had been ruled in personal union by the same branch of the House of Wettin since 1741, after the Eisenach line had died out upon the death of Duke Wilhelm Heinrich.

At the age of 18, he married the Brunswick Princess Anna Amalia, one year his junior and a niece of King Frederick the Great of Prussia.

As Dowager Duchess Anna Amalia actively took up the regency, with the approval of the Empress Maria Theresa and the support of her ethical Minister Baron von Fritsch.

As educator for her sons, she employed the poet Christoph Martin Wieland, who was a professor at the University of Erfurt.

In 1804 Duke Charles Augustus' eldest son and heir Charles Frederick married Maria Pavlovna Romanova, sister of Emperor Alexander I of Russia, a conjugal union which decisively promoted the rise of the Ernestine Saxe-Weimar dynasty.

Though at first an ally of Prussia in the Napoleonic War of the Fourth Coalition, Duke Charles Augustus escaped his deposition by joining the Confederation of the Rhine on 15 December 1806.

After the official merger in 1809, the Duchy of Saxe-Weimar-Eisenach consisted of the separate districts around the capital Weimar in the north and Eisenach in the west.

In the east, it gained most of the Neustädter Kreis [de] (Neustadt district; 629 km2, 243 sq mi) from the Kingdom of Saxony.

It also received most of the Principality of Erfurt, which had been an exclave of Mainz before the war and a directly administered French fief under occupation.

In the Rhön area, the Eisenacher Oberland [de] was created from adjacent former parts of Hesse-Kassel and territories held by the secularized Princely Abbey of Fulda.

Maria Pavlovna, who was grand duchess from 1828, featuring composers like Franz Liszt and Peter Cornelius.

He was married to Sophie, who supported his plans, and he rebuilt the decaying Wartburg the romantic historicism style of the day and had it painted by Moritz von Schwind.

He also supported, albeit half-heartedly, the founding of the School of Applied Arts in Weimar, which merged to form the Bauhaus in 1919.

In 1901 Charles Alexander was succeeded by his grandson William Ernest, who was married to Caroline Reuss of Greiz and later to Feodora of Saxe-Meiningen.

A total of 56% of the duchy's territory was used for agriculture, mainly in the districts Weimar and Neustadt and the exclaves Allstedt and Oldisleben in the Goldene Aue area.

Game was only found near Eisenach, in Eichenzell and in the Ilmenau exclave, where the grand duke's largest hunting ground was located on the banks of the Gabelbach.

In 1846, Carl Zeiss found a precision engineering and optical company that quickly developed into a world leader.

In 1895, there were 23 branch offices of savings banks in the grand duchy, and they were managing deposits totalling approximately 40 million Reichsmark.

The grand duchy was part of the Thuringian Toll Union, except for the exclaves Ostheim, Oldisleben, and Allstedt.