They asked my salary range, what should I say?

A recruiter asked for my salary expectations on a first call as I look for work as a machine operator. This is my first time dealing with any of this. I looked up ranges in Denver and they vary a lot. How do you research fairly?

Thanks for writing this out. I went through something close to it 12 months ago, and it got easier once I kept a simple log of every call and form.