what are my legal options when a new manager is targeting/harrassing me?

I am the most senior employee in my dept. the only female for years, working in a manufacturing company. I have received very high performance ratings and held a unique job in the company - working with government auditors and senior management across the company to meet major company goals. I've received awards and great reviews from sr. managers in the company. A new manager was assigned to our dept. At the first opportunity - he emailed me to tell me that a new, inexperienced young employee would be taking over my technical job. No transition of info would be needed. I asked to meet with him to discuss. I asked why and was told that they didn't need anyone experienced to do this job. I asked what I would be doing and he said oh, you can help out the mechanic. After years of being in a very crucial role, I was put into a job that required mechanical expertise I don't have and knew I was being set up. What can I do?