While it's difficult to pinpoint the exact country with the most Ruby on Rails developers, the United States has a significant number of Rails developers due to its strong tech industry and early adoption of the framework. Other countries with notable Ruby on Rails developer populations include the United Kingdom, Germany, Canada, Australia, and India. The Rails community is global, and developers can be found in many countries across the world. When hiring a Ruby on Rails developer, it's important to consider factors such as language, time zone, and cultural differences in addition to their technical skills and experience.