The All Fifty Club is devoted to honoring those with the time and the drive to set foot in every state in the U.S. Recognizing the monumental nature of the task, the club will consider anyone who has visited 35 or more states a member and award them with a personalized plaque.
Anyone can claim membership, as no proof is required, but as the website says, anyone choosing to lie to become a member has bigger issues to work through. Rather than being an award, the All Fifty Club's certificates are more of a reminder for a personal achievement. As such, there is only one actual rule governing what constitutes a visit: airports don't count.