Yep, Pre-Crisis, J'onn had come from a thriving Martian society that was in many ways eerily like 1950s America. His costume? Those are Martian street clothes, like fighting crime in a trenchcoat and fedora for Earth heroes.
But by this point it had already become implausible that there was life on Mars, so the JLA had a story in which the Martians were unable to sustain their society on Mars anymore (I forget if it was entirely natural or if some sort of disaster precipitated it) and J'onn, as their most experienced space traveler was called back to help out.
I think he didn't come back permanently until the end of the Satellite Era (which the White Martians were partially responsible for.)