The gun originated with a contest between Rheinmetall and Krupp, both of whom entered several designs that were all considered unsatisfactory for one reason or another. In the end the army decided the solution was to combine the best features of both designs, using the Rheinmetall gun on a Krupp carriage.
The carriage was a relatively standard split-trail design with box legs. Spades were carried on the sides of the legs that could be mounted onto the ends for added stability. The carriage also saw use on the 10 cm schwere Kanone 18 gun. As the howitzer was designed for horse towing, it used an unsprung axle and hard rubber tires. A two-wheel bogie was introduced to allow it to be towed, but the lack of suspension made it unsuitable for towing at high speed. The inability of heavy artillery like the sFH 18 to keep up with the fast-moving tank forces was one of the reasons that the Luftwaffe invested so heavily in dive bombing, in order to provide a sort of "flying artillery" for reducing strongpoints.
The gun was officially introduced into service on 23 May 1935, and by the outbreak of war the Wehrmacht had about 1,353 of these guns in service. Production continued throughout the war, reaching a peak of 2,295 guns in 1944.
Several other versions of the basic 15 cm were produced. The 15 cm sFH 36 was a version with a greatly reduced 3,450 kilograms (7,610 lb) weight that was an attempt to improve mobility, but as it used various light alloys to achieve this savings it was considered too costly to put into production. The 15 cm sFH 40 was another improved version, featuring a slightly longer barrel and a new carriage that was suitable for vehicle towing and allowed the barrel to have wider firing angles and thereby improve range up to 15,400 m. However this version was even heavier than the sFH 18 (at 5,680 kilograms (12,520 lb)) and was found to be too difficult to use in the field. Some of these barrels were later fitted to existing sFH 18 carriages, creating the sFH 18/40. A further modification was the FH 18/43, which changed to a split breech that allowed for the use of bagged charges instead of requiring the gunners to first put the charges into shells. Two further attempts to introduce a newer 15 cm piece followed, but neither the 15 cm sFH 43 or 15 cm sFH 44 progressed past the stage of wooden mock-ups.