In 1978 a public referendum on the dam project was held, on August 8, in the 12 eastern Missouri counties affected by the Meramec Park Lake Project, and 64% of the voters opposed the building of the dam. Congressmen who previously supported the dam took note of the vote and voted to deauthorize the project, the only such case in the country where citizens stopped an Army Corps dam already under construction. Ronald Reagan signed the deauthorization bill on December 19, 1981, one and a half years after the death of Dill on August 13, 1980. It was Dill's wish that the state be given the right of first refusal on the sale of the Onondaga property. With cooperation from his survivors and assistance of the Nature Conservancy the state legislature met the Dill family's request, and Onondaga became a state park dedicated to Lester B. Dill. Officially dedicated in 1982, the cave was also designated as National Natural Landmark.