I can think of a handful of major yards on the KCS system:
Knoche Yard (Kansas City, MO)
Deramus Yard (Shreveport, LA)
Gateway Yard (East Saint Louis, IL)
If I'm correct, Knoche and Deramus are the two largest. Knoche is a joint KCS-CP facility. This agreement dates back to the days of the Milwaukee Road. Over the years KCS has shared Knoche with the Milwaukee Road, SOO Line, CP Rail, I&M Rail Link and the Iowa, Chicago & Eastern.