Formation tops were picked in 16,200 wells from the Williston Basin of North Dakota, South Dakota, and Montana. Each formation top was picked using borehole geophysical log data. Many wells in the Williston Basin do not penetrate the entire stratigraphic section and in many other cases the shallow intervals were not logged. In total, there are 141,096 individual picks composing 29 sets of formation tops. Each top set represents a recognizable stratigraphic marker that can be correlated from well to well. The formation tops serve as foundational observations for building the stratigraphic and structural framework of the 3D petroleum systems model. How each formation top assigns to age, lithostratigraphic unit, and modeled horizon is outlined in the "Williston_Basin_Data_Release_Overview.csv" data table in the parent directory of this data release. This is a child item of a larger data release titled "Data release for the 3D petroleum systems model of the Williston Basin, USA".