kragen-history-of-markup
Starting in 1969 and throughout the 1970s, Charles Goldfarb, Edward Mosher, Raymond Lorie, and others created GML, the Generalized Markup Language, at IBM. It was a meta-language for domain-specific document formats with semantic information, which could be used for flexible stylesheet-based formatting (somewhat like other systems around the same time, such as Don Knuth's TEX and Brian Reid's Scribe) as well as more database-like applications, such as composing tables of contents, or searching a corpus of case law by its citations.
Throughout the 1980s, GML was developed into SGML under the auspices of ANSI.
... HTML
XML
CSS
At ETCon 2004, Tantek and Kevin Marks gave a talk entitled "real world semantics" --- before they invented the "microformats" term, but the presentation covers XOXO, XFN, GeoURL, blogchalking, CC rel="license", VoteLinks. Subsequently they held a BoF session which apparently had more than the three participants listed. The next week, they presented a lightning-talk version of the same talk at ConCon 2004. In 2005, Tantek gave an SXSW talk entitled "The elements of meaningful XHTML".