North Park is the northernmost of two topographic basins that constitute a single intermontane structural basin in north-central Colorado. Petroleum exploration began there in 1912 with a test of one of the many folds apparent at the surface in the area. To date four commercial oil and gas fields have been developed in the northeast quadrant of the park. The predominant structural trend is west of north and is the result of a couple produced during Laramide orogeny. Later deformation in the late Miocene or early Pliocene was a result of north-south-oriented stresses. The first recorded deposition in North Park began in the Late Permian. This sedimentation was the beginning of a long sequence of marine and epicontinental deposition. Several excellent pay zones are found in the Mesozoic beds, especially those of Early Cretaceous age. Future discoveries in this small but petroliferous basin depend upon more detailed structural and stratigraphic studies.