At the end of the Middle Ages, the IJ was a long and narrow brackish bay that connected to the Zuiderzee and stretched from Amsterdam in the east to Velsen in the west.

By the seventeenth century, however, access to the IJ became difficult due to sand bars across its mouth, and ships becoming bigger, and it was nearly impossible for seafaring vessels to reach the city of Amsterdam.

The Haarlemmermeer was first, falling dry in 1852, and the largest part of the IJ followed suit between 1865 and 1876, with only a small lake remaining at Amsterdam that was closed off from the Zuiderzee by the Oranje locks.

It cut through the isthmus to connect to the North Sea near the town of Velsen; a new port, IJmuiden ("IJ's mouth") was built at its west end.

[4] In 2018 a German Luftmine (Wohnblockknacker) was found in the river and safely detonated by the Explosieven Opruimingsdienst Defensie (EOD).