Many of the National Park Service streams are often tended by people—experts in their fields—who get excited about nature and history and have a passion for protecting the places held in the public trust. For example, the African Burial Ground (a delightfully active one for such a small site) might share a resource for researching your slave ancestors in Virginia or link to a database that details the machinations of the slave trade. Other feeds may be manned by rangers who can answer history questions for you.