All major histories of what we now call hypertext start in 1945, when Vannevar Bush wrote an article in The Atlantic Monthly called As We May Think, about a futuristic device he called a Memex.

45 years of hypertext's history: from 1945 to 1990, including survey of major early systems. Chapter 3 from Jakob Nielsen's book, Multimedia and Hypertext, describes the major milestones for hypertext, the internet, and the world wide web, including Vannevar Bush's Memex and Doug Engelbart's landmark demo of the online system (NLS.)

Hypertext, broadly defined, is a document which contains links to other documents. Pretty simple in theory, but it’s a concept that has echoed through the minds of innovators for over a hundred years. Engelbart did not invent hypertext. The word itself was used first by Ted Nelson as early as 1965.

Hypertext can be used to support very complex and dynamic systems of linking and cross-referencing. The most famous implementation of hypertext is the World Wide Web, written in the final months of 1990 and released on the Internet in 1991.