At the Congress of Vienna in 1815 Cochem was given once and for all to the Kingdom of Prussia and in 1816 became the administrative centre of the newly created district authority. The crazy days of 1848/49 led to the formation of the "merry democracy of Cochem". Grandiose speeches were made in the Sun and the Customs House (nowadays the Union Hotel). Even today at Carnival time a song can be heard in Cochem telling about the "year when it was Carnival all year round". Between 1869 and 1877 the Berlin privy councillor Ravené had the ruined castle rebuilt according to old plans from 1576.
In 1942 the castle became the property of the state. The rebuilding coincided with the opening of the Kaiser Wilhelm Tunnel, which reduced the "Cochem Hairpin" from 21 to 4.2 km and was the longest tunnel in the Federal Republic of Germany until 1987.Since 1978 the castle has belonged to the citizens of the town of Cochem. The two fishing villages of Cond and Sehl developed independently of Cochem, and for many years Cond belonged to the territory of Stablo-Malmedy imperial abbey. The Moselle bridge was completed in 1927 and in 1932 Cochem and Cond were combined into one town. The stationing of an air force squadron near Cochem in 1956 led to the development of the Brauheck district of Cochem. In the early 19th century the first real tourists came to Cochem, filled with romantic enthusiasm. Foremost among them were English artists who recorded the beauties of the Moselle Valley in their drawings and paintings. The development of Cochem into the first real tourist centre on the Moselle came in the 1930s.