It's not the oldest, but I personally have a bit of love for Claris Homepage.

Low End Mac was designed in it until nearly the bitter end when they switched the actual hosting and content management to WordPress.

A few years after that was written, Apple released iWeb, which still runs on Mac OS X 10.11, but which is less flexible than Home Page, which itself is a lot more akin to Dreamweaver (which includes design but note content templates) than iWeb.