During the late Middle Ages, Gotha was an important market town, located on the Via Regia international trade route. From 1640, Gotha was the capital of an independent petty Duchy. Due to complicated succession laws of the Ernestine line of the House of Wettin, Thuringia was separated into more and more states that got smaller and smaller, consisting of many dismembered territories. In 1826, Saxe-Gotha was merged with the neighbouring Saxe-Coburg.
While their home territories were pretty insignificant, the House of Saxe-Coburg and Gotha were immensely successful in European marriage politics, and at the end of 19th century several European countries were ruled by this dynasty: the United Kingdom (Queen Victoria was married to Prince Albert of Saxe-Coburg and Gotha; the House of Windsor is just another name of Saxe-Coburg and Gotha, chosen during the anti-German sentiments of the First World War), Belgium (Leopold I was chosen as King of the Belgians in 1831), Bulgaria and Portugal (the latter two are now republics).
There was a rivalry between the two main duchies and residences of Thuringia: Gotha and Weimar. While Weimar stood out for its cultural impact, with Goethe, Schiller, Wieland and Herder all present at Duchess Anna Amalia's "Court of the Muses", Gotha became an early centre of natural sciences. The Dukes of Gotha began to collect naturalia in the 17th century and the town's museum of natural history was one of the first of its kind. The Gotha astronomical observatory was established in 1786 and had a Europe-wide leading position at that epoch. Moreover, Gotha was a stronghold of the German publishing sector, with Perthes being Germany's prime publisher of maps and atlases.
The Gothaer Versicherung was Germany's first mutual insurance company, based on English models. In 1875 the Socialist Workers' Party was founded in Gotha, predecessor of the Social Democratic Party of Germany.