The Lauwers, a river that originates in the history of Friesland, is already mentioned in the Lex Frisionum as "fluvius Laubachi," functioning as a border between two areas. In the year 734, the area west of the Lauwers already belonged to the Frankish empire (Westerlauwers Friesland), while the area east of it was incorporated around 785 (Oosterlauwers Friesland).
According to old writings, the Frisians who killed Boniface in 754 came from the Groningen side of the Lauwers, possibly from Suxwerd, the main town of Humsterland.
Even in a donation to the abbey of Echternach in 786/787, there is talk of possessions in Humsterland, located on the other side of the river 'Lauvichi'.
Over the centuries, the Lauwers continued to mark the border between Oostergo, a region connected to Friesland, and the Ommelanden, a region connected to Groningen. Initially, the border was of lesser importance, as there was no central government on either the western or eastern banks of the river.
However, with the rise of the city of Groningen, the river became more important. The city became increasingly important in resolving legal disputes in the deeply divided Ommelanden. Treaties were concluded between the city and the surrounding regions, with the city's position gradually evolving from a lesser partner to a more important partner over time, from wikipedia.