From the Late Middle Ages, the trade with the Baltic Sea was economically very important for the Republic of the Netherlands, and Amsterdam especially. The trade originated in the network of Hanze cities and in the Early Modern Period, Amsterdam soon became a staple market that formed the centre in the trade in goods from the north to the south of Europe and vice versa. The emphasis was on bulk goods. Important products from the Baltic area were wood, grains and iron. From the south came salt, wine and luxury goods, amongst other things.

This trade was so important for the Republic that it received the name 'moedernegotie', i.e. the 'mother of all trades'. The economy of the Netherlands was based on this trade for a long time and the profits from it formed the basis for the early colonial expansion. Over the centuries, several wars were waged over the control of this trade, mostly over the narrow entrance to the Baltic Sea, the Sound.

A toll was levied in the Sound, based on the loading capacity of the passing ship. This trade and toll were of such importance, that a specific ship type was developed for it in the Netherlands: the flute (fluit). Because the loading capacity was calculated along the surface of the upper deck, the Dutch started to build flutes with a board that progressed inward to manipulate the calculation of the tolls to be paid (because it resulted in a smaller surface of the upper deck). In this way, the flutes had a larger cargo hold then which they paid tolls for.

The toll registers of the Sound form an important source for the research into this trade. These registers are the archives of the tolls levied by the Danish crown in the Sound. These can be searched digitally in their entirety at https://www.soundtoll.nl/