Further, even if your county fair's category does exist at the State Fair, and you put that category down as your choice, you still may end up in a different one. This happens to about 20% of all projects in the Fair. A committee of experienced judges assigns each project in the Fair to its proper category based on their reading every Project Summary in the Fair. The goal of this assignment is to insure that projects which are similar end up in the same category.
So, what do you do? Pick the category which fits the subject of your project the best. Remember that the category concerns the subject of your study, not its methods or its eventual intended goals. See here for more guidance.