Erin Malone, who helped create Yahoo!’s pattern library, gives a fantastic timeline of modular UI design.

I especially love her emphasis on people sharing what they know, which is how ideas evolve and take root:

It’s important to not forget about the explorations and experiments and hard work that many people did (in their companies and on their own time) to share their knowledge and to advance the conversations and the practice of user experience design. Without this work, no one today would be so easily accepting of the need for a robust style guide that contains interactions and code.