WorldCat:

WorldCat is a worldwide catalog of 56 million items found in 9,000+ libraries, including State Library & 25+ SD libraries. Lists & locates books, journals, computer files, Internet resources, music, recordings, archival materials, maps, audiovisuals, etc.

WorldCat is available on personal computers located within SD libraries and on SD campuses (academic, K-12, & SD government). In addition, individual South Dakotans may use any of the 14-digit library cards issued by any of the 70+ full/associate member libraries of SDLN to access WorldCat remotely. SD State Library cards (which may be requested online) can be used by individuals to access WorldCat. [Hint: typically, the password assigned to these 14-digit library cards is the last name of the person.]

Users: You will be asked for your username and password to access. This is your State Library Card or SDLN Member Library Card barcode and password. If you need your password, you may call the State Library at 1-800-423-6665 (SD Only) or 605-773-3131 or your local library.
Funded by South Dakota taxpayers and by federal Library Services & Technology Act/LSTA monies, the SD State Library makes WorldCat available free-of-charge throughout SD. There is a limit of five simultaneous users throughout South Dakota. So, please exit promptly in order to allow other users to have access.

For Librarians, additional information on WorldCat is available.
WorldCat website