There are many conceivable ways to divide up theme parks. In fact they often range from billion dollar mammoth complexes to small mom and pop operations, supported by the local community. One obvious way to distinguish between these parks is by state.
The definition of what is a theme park can change by state. More sparsely populated states may not have anything that meets the conventional definition of a theme park, or which compares to Disneyland, but they may consider them theme parks for their purposes.