SO CAL ROTAX CHALLENGE has argueably the most competitive Masters karting in the US
So Cal has two strong series with relatively large Masters grids: LAKC has already been mentioned, the other is the So Cal Rotax Challenge. This year the Masters class started off big time with 14 entries for the first race and 21 entries for the second race. There is coverage on this race on ekartingnews.com home page.
The So Cal Rotax Challenge races are spread across 3 different tracks in Southern California and in the past So Cal Masters grids have had 2 or 3 Rotax National Champions in attendance.
Come race the So Cal Rotax Challenge and get your butt run over by most of the grid.