The residence palace of the Nassau dukes, today the seat of the Hessian state parliament, was built from 1837-42 in the neoclassical style on historic grounds in the center of Wiesbaden according to plans by the Darmstadt architect Georg Moller. The exterior of the city palace was completed in 1840 and the interior was finished in 1843. The on-site construction manager was Richard Goerz, who had been the court architect since 1840.

For the newly founded Duchy of Nassau (1806), the existing buildings of the castle and the Renaissance palace built at the end of the 16th century and extended again were neither sufficient nor sufficiently representative. Soon after taking office, Duke Wilhelm therefore planned to build both a separate ministerial building (government building) and a new city palace. Initially, the intention was to build the city palace in the intended line of sight to the Biebrich residence on the northern edge of Luisenplatz, where the church of St. Boniface stands today. Here one could have built freely in the baroque style of absolutist rulers. However, the enlightened Duke Wilhelm chose the location near the old Nassau castle in the middle of the city, no doubt also in view of the historical reference. Architect Moller had to fit the new building into the front of the existing buildings on the cleared corner plot in such a way that a palace complex facing the citizens and documenting the open nature of the Nassau rulers was created. This was to serve exclusively the residential and representative purposes of the ducal family. Duke Wilhelm died in 1839 before the palace was completed. Only his son Duke Adolph zu Nassau was able to move the Nassau residence from Biebrich to the new city palace at the end of 1842.

Moller came up with an original solution with the diagonal development of the site. The main building with plinth and first floor, two upper floors and a final attic consists of two nine-axis wings arranged at obtuse angles on Schlossplatz and Marktstraße, flanking a semi-circular protruding central risalit. An entrance is located on the outer axis of each wing. While the second floor of the main building is emphasized as the bel étage by a more elaborate design, the central risalit is distinguished by the entrance, which is only used on prestigious occasions, and an altar resting on six columns as well as the Nassau coat of arms above the middle window of the second floor.

Behind the main building is the so-called connecting building. This consists of a rotunda in the middle of the diagonal of the main building with a hall on the first floor and the former dining hall (also known as the domed hall) on the upper floor. The hall is connected to the entrances of the main building via arched, open arcades on both sides of the hall. This was originally accessed primarily via the passageway. From the hall, one then passed through a vestibule into the representative grand staircase of the main building. Above the arcades are glass galleries used by Duke Adolph as conservatories.

At the same time as the main and connecting buildings of the palace, a four-winged complex was built to the north-east of them, around whose inner courtyard the stables, riding hall (demolished in 1960), coach house and a connecting wing were grouped. The palace's largest banqueting hall, the concert hall, was built above the coach houses.

In contrast to the rather plain design of the main façade, the interior of the palace was extraordinarily splendid. The preserved historical rooms and halls bear witness to this. Numerous artists, artisans and craftsmen were involved. The furniture manufacturer and interior decorator Anton Bembé and the decorative painters and brothers Ludwig and Friedrich Wilhelm Pose, who ingeniously decorated the rooms of the castle with arabesques, flower paintings and more, deserve special mention. For example, the original dance hall (now the Small Hall) was painted with depictions of Pompeian dancers. The sculptors Johann Baptist Scholl, whose works include the Nassau coat of arms, and Ludwig Schwanthaler, who created the statues of the gods in the grand staircase and vestibule, as well as the statues of the "Spanish Dancers" in the large dining room, are also worthy of mention. The artistic design of the ceilings, including shadow painting, and the inlaid floors, which are designed in ever-changing patterns and made from a wide variety of precious woods or different colored marble, provide an intense insight into the craftsmanship of the time.

After the annexation of Nassau (1866), the palace served as a stately residence for the Hohenzollerns when they visited Wiesbaden every year. It is thanks to them that they left the Nassau ambience and the former insignia, in particular the Nassau coat of arms, untouched. In 1918 the French and in 1925 the British occupying power took over the government in Wiesbaden. In 1930, the palace came into the possession of the Prussian Palace Administration and was used as a museum until the beginning of the Second World War.

During the war, the palace was the seat of a general command of the Wehrmacht. Severely damaged in a bombing raid on Wiesbaden in February 1945, the building was restored and became the seat of the Hessian State Parliament, which was elected on December 1, 1946. Changes, additions and new buildings in recent decades have left the old building largely untouched. Both the façade of the main building and the interior rooms from the Nassau period have retained their historical ambience.