Schloss Lenzburg was first mentioned in 983 as a master seat of the Grafen von Lenzburg, who at that time meaning Lehensherren in the Swiss mainland. In 1173, this was assigned it as Lehen to Kyburger. In 1230, at the foot of the schloss, a market settlement was created. It lasted until 1273 up to the conquest of the Aargaus by the oath comrades in the year 1415 by Habsburg, Austria. From 1444-1788, Landvogt governed. In 1804, one year before the Canton of Aargau was formed, ownership of the castle was transferred.
The castle had been rented from the canton for the following period, until its sale in 1860. For the following period the castle had several owners, including the father of the German poet Frank Wedekind. In 1893 the American owners renovated the castle. In 1956 the canton finally acquired the castle, and converted it into a historical museum.
The Landvogtei became the office and house of the Bernese Landvoegte. An older structure was destroyed in 1518 by a fire.
The current home of the museum's offices.
Literally, the "East Bastion," it lies at the eastern edge of the inner court. It was built during the Thirty Years' War to close the gap between the palace and the Landvogtei and to protect the castle against cannon bombardment. After deteriorating, it was replaced by a rose garden under the ownership of American August Edward Jessup.
Currently home to a Café, the palace was originally built by Grafen von Lenzburg in 1100.
This building's construction began under Habsburger rule in 1340.
The tower was built between 1150–1170 by the Grafen von Lenzburg to the palace. The owner died during the work and the building remained unfinished during almost 200 years. The tower was not finished until 1344. The area has been a prison since the 17th century on the first upper floor. It is still visible today for tourists visiting the museum. In 1900 the tower was reconstructed by its American owner and received its current appearance.