Check out this interactive map by the NATIONAL CENTER FOR FARMWORKER HEALTH which maps out the H-2A employer certificates for 2015. From this data you can indicated the number of farm workers and see where they predominantly work.
Agriculture has few safety regulations which is problematic for farm workers. According to the federal standards children 10 years of age can be employed as a farm worker with parental consent and children 14 years of age without parental consent or a work permit. For these reasons farm workers face various health issues including occupational injuries from chemical exposures and musculoskeletal disorders, chronic conditions (diabetes and heart disease), infectious disease (tuberculosis and sexual transmitted infections), mental health and child developmental issue.
Maps like this allow for public health workers to identify highly concentrated areas and possible provide resources, such as health services, to such vulnerable communities.
By Julia Watson