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History

The first connection between the North and Baltic Seas was constructed while the area was ruled by Denmark–Norway. It was called the Eider Canal and used stretches of the Eider River for the link between the two seas. Completed during the reign of Christian VII of Denmark in 1784, the Eiderkanal was a 43 km (27 mi) part of a 175 km (109 mi) waterway from Kiel to the Eider River's mouth at Tönning on the west coast. It was only 29 m (95 ft) wide with a depth of 3 m (9.8 ft), which limited the vessels that could use the canal to 300 tonnes.

After 1864, the Second Schleswig War put Schleswig-Holstein under the government of Prussia (from 1871 the German Empire). A new canal was sought by merchants and by the German navy, which wanted to link its bases in the Baltic and the North Sea without the need to sail around Denmark.