Knott's Scary Farm is the Halloween version of the park, running on selected nights from late September through October. Started in 1973, it claims to be the original theme-park Halloween event — predating Disney's and Universal's by decades — and is still one of the largest, with a thousand monsters roaming the grounds, half a dozen elaborate haunted mazes, and the lights mostly off.
Tickets are sold separately from regular daytime admission. It is not appropriate for young children; the actors are aggressive and the special effects can be genuinely startling.