The selection, acquisition, and management of digital data are now part and parcel of the work librarians handle on a day-to-day basis. While much thought goes into this work, little consideration may be given to the long-term preservation of the collected data. Digital data cannot be retained for the future in the same way paper-based materials have traditionally been handled. Specific issues arise when archiving digital data and especially geospatial data. This article will discuss some of those issues, including data versioning, file size, proprietary data formats, copyright, and the complexity of file formats. Collection development topics, including what to collect and why, will also be explored. The work underlying this article is being done as part of an award from the Library of Congress's National Digital Information Infrastructure and Preservation Program (NDIIPP).