Clayton, John Middleton (1796-1856), was an American political leader. He served as United States secretary of state in 1849 and 1850, under President Zachary Taylor. As secretary of state, he negotiated the Clayton-Bulwer Treaty of 1850. In this pact, the United States and Britain agreed to protect the neutrality of a canal to be built through Central America. The treaty helped the two countries avoid war over the proposed canal. See Clayton-Bulwer Treaty.