Calw was first mentioned in records in 1075. In the 11th century the town grew around the older castle of the Grafen (Earls) of Calw. In the Middle Ages Calw was an important commercial town especially for the trade of cloth and leather. In 1345 Calw became part of W�rttemberg and by the 16th century had become the summer residence of the Duke of W�rttemberg. In the 18th century Calw flourished from the lumber trade and rafting of timber on the river Nagold.
Due to her romantic relationship with a Polish guest worker, seventeen year-old Calw resident Erna Brehm was publicly shaved bald in the town's market square in August 1941. She served eight months in jail in Calw and Stuttgart for violating Nazi Rassenschande ("racial shame") laws before being deported to Ravensbr�ck concentration camp. She was released on 1 April 1944 because she was in such poor health that she was no longer able to work. She was extremely underweight (reportedly only 34.5 kilograms or 76 pounds) and died on 19 August 1951 at the age of twenty-seven.
During World War II, a small subcamp of Natzweiler-Struthof concentration camp, where parts for aircraft where assembled by female forced laborers, was located here. The most prominent resident of Calw was the author and Nobel prize winner Hermann Hesse.
The district reform of 1 January 1973 gave Calw its current size. It became a part of the newly founded Northern Black Forest Region, which itself was assigned to the administrative region of Karlsruhe. On 1 January 1975 Calw was combined with the municipalities of Altburg, Hirsau and Stammheim into the town of Calw-Hirsau. On 1 January 1976 it was renamed as Calw
