Geoscientists use spatial thinking skills in many common tasks, such as adding a third dimension to two-dimensional maps by drawing cross-sections or envisioning rock fabrics from a single hand sample or exposure. Field courses allow students to practice and develop those skills in authentic settings. This study examines the development of spatial perception and geoscience-specific penetrative thinking skills, as measured by paired pre- and posttests using the water-level test and the Geologic Block Cross-Sectioning Test, in a sophomore field mapping course. Students began the course with strong spatial perception skills, but developed their penetrative thinking skills significantly (p < 0.0001) between the beginning and end of the course. Furthermore, the gender gap in penetrative thinking skills that existed at the beginning of the course was eliminated by the time the course ended. This work can be used as a baseline for comparison with results of nonfield-based exercises that are designed to develop geologic penetrative thinking skills in other ways.