According to Matt Stone and Trey Parker, the line "god damn Mongolians tear down my shitty wall" was created while they were visiting the Great wall of China during the 90's.
In one scene, a man asks Tweek about directions to Breckinridge. In Trey Parker's first full-length film Cannibal! The Musical (1993), Alferd Packard and his party are en route to Breckinridge.