They started it in 2013 or 2014. It's a rivalry trophy that Spurrier, I think, pushed for during Missouri's first year of two in the SEC.
If I'm correct, i think the mayors of both Columbia, MO, and Columbia, SC, went in on getting the trophy for the universities to use for the game or something.
It's clearly minor, but it also kind of works for these two teams (Missouri looking to create newer in-conference rivalries following the move, and South Carolina has often tried - unsuccessfully - to create a stronger in-conference rivalry tie since their move to the SEC... and in their case UGA has been about it, but even that's felt a bit more one-sided on USCe's end than on UGA's end).