Katwijk aan Zee emerged from the Reformation as a staunchly Protestant town, a reputation it still has today. It's also named to be an enclave of the Dutch Bible-belt ('Bijbelriem') that covers the area from the North-South side of Holland ('Zeeland') to Middle-East, where there's the Veluwe forest. The main religion in the Bible-belt and therefore also in Katwijk aan Zee is a strict form of Calvinism.
Amplified by the strict form of religion, the differences with neighboring communities and the non-migratory nature of members of the old Katwijk families, Katwijk aan Zee continued its existence as a quiet, close-knit North Sea fishing village from the 16th century. Although fishing is not a major activity in the village today and many of the inhabitants are nowadays secular, the old traditions still survive in many ways. Most of the inhabitants are still very traditional, whether they are member of a Calvinist church or not.
Katwijk aan Zee had its own unique dialect, called 'Katwijks' or 'Strand-Hollands' ('Kattuks' in dialect). This dialect is still spoken by a considerable number of people, therefore being one of the few active dialects of Hollandic still in active use. Yet, fewer youngsters learn to speak the dialect actively.
Over the course of time the mouth of the Oude Rijn silted up. However, a lock was constructed at the mouth of the river in 1807 by engineer F. W. Conrad (d. 1808). After this the Old Rhine (here called the Uitwateringskanaal) did not flow naturally into the sea, but was held back by a lock. When necessary, the lock can be opened to allow the river to flow out to sea. The shore and the entrance to the canal were also strengthened by dikes.
During World War II, most of the buildings of Katwijk aan Zee were demolished by the Germans to make way for the Atlantic Wall. In the dunes south of Katwijk, many bunkers War II can still be found.
