FSKC's previously highest-rated telecast came on April 26, 2015, and came in at 17.3.
Tuesday night's game bested the ABC, CBS, FOX and NBC affiliates' combined (16.1) during the game (7-10:45 p.m.).
The Royals' local-market ratings rank No. 1 in Major League Baseball.
Jeffrey Flanagan has covered the Royals since 1991, and for MLB.com since 2015. Follow him on Twitter @FlannyMLB. This story was not subject to the approval of Major League Baseball or its clubs.