What are my rights if I was demoted and my pay cut by 35% but I never received written notice?

Did this action violate the terms of any employment contract or union agreement? Did is constitute some form of legally actionable discrimination? If not, then as an "at will" worker, it was perfectly permissable. The fact is that most companies can set the conditions of the workplace much as they see fit. This includes making demotions and decreasing pay. Further, such action can be taken with or without notice. That is for any time to be worked going forward. Any pay earned before you were notified of the change must be paid at your old wage. In other words, such a reduction cannot be made retroactively.

You don't have any rights unless you had a written employment contract for a definite term (e.g. a one-year contract) which is still in force or effect and which guaranteed your position and/or pay. If you did have such a contract and this violated it, you could sue your employer for "breach of contract" to enforce it (e.g. for monetary compensation for the breach). However, in the absence of a written employment contract, you were an "employee at will" and your employer could legally demote you and/or reduce your pay at any time, for any reason, withouit any prior notice. An employee at will has no rights in or to his or her job, or his or her title/position, or his or her pay--it's all up to the employer's sole discretion.