Rangers' celebrations were put on hold after a goalless draw at Montrose, but they were crowned champions when closest rivals Queens Park were beaten by Elgin.
The achievement marks the completion of stage one in the club's rebuilding process after liquidation resulted in the Ibrox club losing their SPL status and being demoted to the bottom tier last summer.
Skipper McCulloch: "There was obvious disappointment after the game, it didn't flow and we didn't play as well as we can. But to hear on the bus that we were champions was the best feeling in the world.
"I've been lucky enough to win three titles before but I think this is my favourite one. I've been lucky enough to be captain for this one and it means the world to me and my family.
"We can only play against the teams we've been told to play against but, at the end of it, if you are giving me a winner's medal I am taking it.
"It really is a dream come true to captain the team and hopefully we can kick on now. This will definitely stay with me for the rest of my life - to captain a Rangers team to win a league means the world to me.
"I think the low points this season, the hard times, have made the boys stronger for next season, that's the way I look at it anyway."