In order to secure a more satisfactory transit treaty of _isthmian transit than the ar rangement which had been negotiated in 1844, the American government concluded a treaty in 1846 providing for equality of use of the transit route for the commerce and citizens of both countries under American guarantee, really establishing an American protectorate over the isthmus, but for a commercial purpose in which all the world had a common interest, and with expectation of similar guarantees by Great Britain and France. It became effective on 10 June 1848. In 1847 in reply to invitations for protection against the apprehended Flores expedition, Secretary Buchanan reported that Spain through Calderon had disavowed to the American government any part in the proposed expedition — thus indicating her abandonment of intention to encourage similar exueditions and removing a main source for apprehension of serious dangers. Later, in May 1848, he as sured Ecuador (through instructions in opening regular diplomatic relations) that the American government on every occasion would employ at least all the moral means within its power to discourage and arrest intervention or dictation of European governments in the affairs of in dependent states of this American hemisphere.
The matured Latin American policy of the Polk administration was expressed by Secre tary Buchanan on 1 June 1848 in dip lomatic relations with Bolivia, the only inde wdent Latin-American country to which the United States had not previously sent a Min ister. Urging the necessity of the establish ment and maintenance of an American system of policy for protection and security, and em phasizing the fact that °Liberty cannot be pre served without order,") he especially hoped that Peru in order to prevent future irritation and dissension would agree to cede the port of Arica to Bolivia. Possibly encouraged by President Taylor's expression of the American general policy in 1849, Venezuela in 1851 pro posed that the United States should form an alliance "or at least take a more decided stand to protect the South American republics)" In the decade after 1850, the period of American clipper-ship activity in the Pacific, the American government actively used diplo macy to secure protection and expansion of commerce with Latin America — at the same time continuing a policy of securing respect for American commerce by enforcement of American claims for injuries to persons and property. Among the most important subjects of diplomatic negotiation besides claims were the conditions of the guano trade on the west coast, the danger of European influence, the opening of South American rivers to foreign commerce and the conditions of transit at Panama.
In 1852, in connection with difficulties re sulting from restrictions on the guano trade, the American government, through Secretary Webster, took steps to protect American inter ests on the detached Lobos Islands which had been visited by American seamen for half a century, but after an investigation of claims of title soon decided through Secretary Everett to yield to the protests of Peru. In 1858, during the Vivanco insurrection in Peru, a diplomatic dispute arose over the rights of American ves sels to obtain guano at the Chinca Islands in connection with the Peruvian seizure of two guano vessels, and resulted in the suspension of diplomatic relations in 1860.
The American acquisition of the Gallipagos Islands from Ecuador, suggested about 1852, was apprehended by Spain, France and Great Britain late in 1854 in connection with an American draft treaty with Ecuador, which was regarded as establishing an American pro tectorate over the islands which had long been important in connection with American com mercial interests in the Pacific. At that time
Ecuador, still apprehensive of the plans of General Flores, urged the necessity of eternal vigilance to prevent vast schemes for European ascendency in South America, and apparently New Granada desired the American government to adopt a more liberal policy of sustaining and protecting the nations of South America. The American Minister (Clay) at Lima, convinced that the United States would be forced by cir cumstances to interfere in the affairs of other states, urged his government to adopt a more effective foreign policy in relations with Span ish America and the establishment of a control ling influence in the western hemisphere. By 1856 there was a decided decline in South American friendliness toward the United States —a decline which resulted largely from the filibustering schemes of William Walker in Central America and which found expression in the °Continental Treaty") signed at Santiago de Chile by representatives of Chile, Peru and Ecuador and designed to form a closer rela tionship of all Latin American republics. In 1857 the American Minister (Dana) in Bolivia, desiring to create a better Latin American feeling toward the United States, suggested to his government that the basis of the American fixed policy should be the Monroe Doctrine, nonexpansion southward of the Gulf and treaties of alliance guaranteeing the integrity of Spanish America.
In the opening of South American rivers the American government took an active part through diplomacy. In October 1852, after the defeat of the Argentine dictator (General Rosas) by the governor of Entre Rios, it ob tained the navigation of the Parana and the Uruguay, which were opened to the merchant vessels of all nations by General Urquiza (pro visional director of the Argentine confedera tion), a privilege later confirmed by treaties with the United States, Great Britain and France in July 1853. At the same time it began preparatory negotiations to secure for Ameri can vessels the navigation of the Paraguay River and upper Parana which, after vari ous difficulties resulting in an American naval demonstration, Paraguay was finally induced to grant in 1859 by treaty. Its efforts to ob tain the consent of Brazil to the opening of the Amazon, first contemplated even before 1850, begun in 1851 by instructions to naval officers to explore the river from Peru east ward and report its facilities for navigation and its opportunities for commerce, and in volving a series of negotiations with Peru and Bolivia and with other countries on the upper waters of the river, reached partial success in 1858 by a treaty with Bolivia guaranteeing the United States access to Bolivian ports on the upper Amazon, and finally attained full success in the Brazilian decree of 1866 declaring the Amazon and its tributaries open to the corn, merce of all nations. Relations with New Granada concerning the Panama transit route across which an American railroad had been completed in 1855 were especially irritated in 1856 by a riot at Panama, resulting in a series of claims which were not finally settled until 1866. Following the riot Secretary Marcy, de siring to facilitate and protect the transporta tion of persons and property across the Isthmus, proposed to New Granada -a new treaty for lease and cession of a belt of land 20 miles wide from Atlantic to Pacific, and certain is lands in the Bay of Panama for use as naval stations, but New Granada declined to negotiate such a treaty.