Hohenzollern Castle
The current castle was built by Hohenzollern scion Crown-Prince Frederick William IV of Prussia. Traveling through southern Germany en route to Italy in 1819 he wished to learn about his family's roots, so climbed to the top of Mount Hohenzollern. He would write in 1844 as King:
He engaged Friedrich August Stüler, who had been appointed Architect of the King for the rebuilding of Stolzenfels Castle in 1842 while still a student and heir of Karl Friedrich Schinkel, to design a new castle. Stüler began work on an ornate design influenced by English Gothic Revival architecture and the Châteaux of the Loire Valley in 1846. The impressive entryway is the work of the Engineer-Officer Moritz Karl Ernst von Prittwitz, considered the leading fortifications engineer in Prussia. The sculptures around and inside the castle are the work of Gustav Willgohs. Like Neuschwanstein Castle in Bavaria, Hohenzollern Castle is a monument to German Romanticism which incorporated an idealized vision of a medieval knight's castle. Lacking some of the fantastic elements and excesses of Neuschwanstein, the castle's construction served to enhance the reputation of the Prussian Royal Family.
Sigmaringen
In 1632 the Swedes occupied the castle during the Thirty Years' War. 
From 1806 to 1849 Sigmaringen was the capital of the sovereign Principality Hohenzollern and residence of the princes of Hohenzollern. 
As a result of the Revolution in Sigmaringen of 1848, the Princes of Hechingen and Sigmaringen waived on their rule, whereby both principalities in 1850 fell to Prussia. From 1850 to 1945 Sigmaringen was the seat of Prussian Government for the Province of Hohenzollern. Karl Anton von Hohenzollern was 1858-1862 Prime Minister of Prussia. 
From 1914 to 1918 around 150 men from the town lost their lives during World War I. 
In the Nazi era a Gestapo office was in Sigmaringen. Since 1937 it belonged to the Gestapo Stuttgart.