Who's This? The cowboy on page 13 of Who's Who vol.XXIV.
How you could have heard of him: James Robinson cemented the link between Matt and Brian Savage in his Starman series. Matt and other western heroes had a cameo in Armageddon: The Alien Agenda #3 (1992), Infinite Crisis #6 (2006), and DCU: Legacies #3 (2010).
Example story: Western Comics #80 (1960) "The Texas Trail Robbery" by Gardner Fox, Gil Kane and Joe Giella
Not a bad tale, I must say, well drawn and scripted, with lots of procedural details. So many western features turned to aliens and monsters in the Silver Age, it's a comfort to know there were still straight westerns being made, even if they didn't manage to sustain this particular title very long. Perhaps that's why Trail Boss Matt Savage isn't really remembered today. Decent, but no gimmick to make him memorable.
Who else? Maybe we're due for a Flash villain? Because not all Rogues were created equal.