When did you turn atheist?

This might get buried but one person will be good for this answer. Some background: I live in the bible belt, Georgia to be a fact, I notice everyone is religious but not college students (some are but not science majors) I stated questioning god after high school because all the evidence i learn in school says god is not real. When I took Biology in college, I learned that you can trace all organism to a single cell thus making the theory of evolution a fact for me. Why did you turn atheist. Sorry for the horrible grammar.