Question: Lepidium arbuscula is a rare species of flowering plant in the mustard family known by the common names `anaunau and Waianae Range pepperwort, it is endemic to Hawaii, where it is known only from the Waianae Mountains on the island of Oahu, Hawaii (  Hawaiian ) is the 50th and most recent state to have joined the United States of America, having received statehood on which date?
Sentence (from "Hawaii"): Hawaii is the only U.S. state located outside North America.
Relevant evidence: No