A key chapter in Internet history is coming to a close.

Yahoo (YHOO) plans to shut down Yahoo Directory this week, quietly ending a service that was once the primary way to search for information online.

Before it was a search engine, Yahoo started out as "Jerry and David's Guide to the World Wide Web" in 1994. It was essentially a list of websites organized by category that Yahoo founders Jerry Yang and David Filo put together in graduate school.

That list morphed into Yahoo Directory and became one of the most common ways to find information in the early days of the Internet.

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All that changed when search came on the scene, and Yahoo Directory's usefulness faded.

Yahoo added search that searched websites for keywords. In 1998, Google (GOOGL) developed an algorithm for organizing search results by how many other sites were linking to certain Web pages. A few years later, Google became synonymous with searching the Internet.

Still, Yahoo kept its Directory alive for nearly 20 years.

Yahoo unceremoniously announced the end in a September blog post entitled "Progress Report: Continued Product Focus." The post said Yahoo would "retire" the directory on Dec. 31, 2014.