It is available when the mark has only been used intrastate. It provides notice to third parties who conduct state or nationwide searches. It may act to deter others from adopting a similar mark. Is enforceable in state court.
Some states require companies to be registered to do business in that state.
Protection is only statewide. It does not preempt federal registrations. There is no evidence in the Patent and Trademark Office that show the use of the mark, or answers the question of the federal registerability of the mark.