American national parks are fertile grounds for astronomy and planetary science outreach. They are some of the last remaining dark-sky sites the typical visitor (both U.S. and international) can still experience easily. An internal National Park Service (NPS) study shows a dark starry sky is an integral part of what visitors consider their park experience. As a result, the NPS Night Sky Team (a coordinated group of park rangers and astronomers) is measuring and monitoring the sky brightness over the parks in an attempt to promote within the park service protection of the night sky as a natural resource. A number of parks (e.g. Grand Canyon National Park) are currently expanding their night sky related visitor programs in order to take advantage of this resource and visitor interest. The national parks and their visitors are therefore an ideal audience fully “primed” to learn about aspects of astronomy or planetary science that can be, in any way, associated with the night sky. As one of the astronomers on the NPS Night Sky Team, I have been working with park service personnel on ways to target park visitors for astronomical outreach. The purpose of this outreach is twofold: 1) Strengthen popular investment in preserving dark skies, 2) Strengthen popular investment in current astronomical research. A number of avenues already being used to introduce astronomy outreach into the parks (beyond the simple “star party”) will be presented.