There has been a bridge at the location of Bridge 6 for centuries. The bridge is already drawn on Joan Blaeu ‘s map from circa 1649, but this bridge has also been drawn as a pick-up bridge on Balthasar Florisz’s map. van Berckenrode from 1625, then between the Mole Steech (The Palace on Dam Square was not completed as a town hall until 1665) and Mole Street. Later a permanent fixed bridge was built here in 1876; the slopes were too steep for normal traffic (think of horse and carriage and steep hills!). George Hendrik Breitner painted the bridge as a vault bridge.
Although the Gasthuismolensteeg was one of the busiest streets in Amsterdam (it was one of the first streets to have one-way traffic in the 17th century), until the opening of the Raadhuisstraat, relatively little is known about this bridge. It was regularly maintained and widened, because it was part of the (almost) fixed routes that kings and queens used on their journeys through the city, including the coronation of Wilhelmina of the Netherlands in 1898. In 1995 the bridge was named a municipal monument.
The bridge was given the unofficial name Gasthuismolenbrug, a name after the street, which is in turn named after a mill, which was demolished sometime at the end of the 16th century. The mill stood where the current Paleisstraat crosses the Singel. Gasthuis refers to the Sint-Elizabethsgasthuis, which also stood here. In 2016, the municipality withdrew all unofficial names and the bridge has since through life anonymously (referred to only by a number). One of the reasons for this is that bridge 218 was also nicknamed Gasthuisbrug, a reference to the Binnengasthuis, which could be confusing and then to make things a little more complicated Utrecht has an official Gasthuismolenbrug.