It was developed by the firm of Hanomag in Hanover who delivered a total of 99 engines of this class.
Although at the time superheated technology was widespread, the state of Prussia still wanted to have saturated steam engines delivered by Hanomag.
As a result, the performance of the S 9 was little better than the considerably smaller superheated locomotive, the Prussian S 6.
Nevertheless, the S 9 initially formed the backbone of express train services from Berlin to Hanover.
Like all German Atlantic locomotives, the S 9 quickly proved too underpowered for the increasingly heavy trains it had to haul.