Tony gave you the link to USDA which will be your best place to start. There are specific areas which are or are not eligible based on their rules. Become familiar with the rules and make sure you fall in the income guidelines USDA has established to qualify for the program.
If you work with an agent who is also knowledgeable with the guidelines and your wish list for a new home, they can perform a more detailed search and filter out some which may not fit your wish list or the program guidelines. You should have your own representation in your purchase anyway, I'd recommend sooner is better than later.