The National Organic Program (NOP) accredits private businesses, organizations and State agencies who will certify organic producers and handlers. To help you locate an agency, NOP provides an easy to search listing of all agencies.
Currently, there are 52 domestic organic certifying agencies in the United States and also 41 foreign accredited certifying agents. That said, unless you're planning on selling into foreign markets, closer is better. A major benefit of a nearby agency is that it can assist you in getting the help you need, quickly, during the certification process.
Keep in mind that the number of U.S. organic certifying agencies can easily change. If you considered certification last year, and had an agency in mind, you'll need to check their USDA standing via the link above, as agencies can lose their certification accreditation.
Another way to find a decent organic certifying agency is via word-of-mouth. Talk to other farmers or business owners who certify products that closely relate to what you grow or manufacture. See if you can get the honest scoop on nearby agencies from your peers.
It's one matter to locate an agent, but another thing entirely to find the right agency and agent to meet your needs. If you're not sure how to find the best agent to meet your needs, read the following: Issues to Consider When Choosing an Organic Certification Agency.