LaTeX, now that's a layout language.
SGML just provides a framework for marking things up.
ETA: No, I do remember those days. I had a Star LC-10 and then an LC24-10 (24 pins! Swanky! Could do proportional spacing!) and I drove them from a variety of software packages which you've never heard of, including View, WordWise, WordWise Plus and Impression Publisher II, running on hardware platforms you've never heard of, including the BBC Micro, BBC Master, Acorn Archimedes and A5000.