**400** Approximate number of libraries operated by the National Park Service (NPS). **3.5 million** Number of materials housed in the NPS History Collection at the Harpers Ferry (W.Va.) Center for Media Services. The collection includes art, documents, photos, sound recordings, uniforms, and other objects. **25** Number of parks represented in the Open Parks Network, a collaboration between Clemson (S.C.) University and NPS, funded by the ­Institute of Museum and Library Services, to digitize archival materials from parks and other historical sites. The collaboration has so far digitized more than 350,000 objects and 1.5 million pages. **1923** Year that Yosemite Research Library (YRL) began acquiring its collection. One of the oldest NPS libraries, YRL—located within Yosemite National Park in California—has more than 10,000 books. **3,100** Number of preserved plants in the herbarium at Zion National Park in Utah.…