This isthmus route became for a time the prime object of American diplomacy. The United States made in 1846 satisfactory arrangements with the Republic of New Granada (later Colombia), across which lay the most southern route, and in 1853 with Mexico, of whose northern or Tehuantepec route many had great expectations; but a further difficulty was now discovered. The best lanes were those of Panama and of Nicaragua. When the discovery of gold in California in 1848 made haste a more important element in the problem, "Commodore" Vanderbilt, at that time the shipping king of the United States, devoted his attention to the Nicaragua route and made it the more popular. Here however, the United States encountered not only the local independent authorities but also Great Britain. Just to the north of the proposed route Great Britain possessed Belize, now British Honduras, a meager colony but with elastic boundaries. For many generations, too, she had concerned herself with securing the rights of the Mosquito Indians, who held a territory, also with elastic boundaries, inconveniently near the San Juan River, the Caribbean entrance to the Nicaraguan thoroughfare. From Great Britain, moreover, must come a large portion of the capital to be employed in constructing the canal which was expected soon to cut the isthmus. The local situation soon became acute. Costa Rica, Nicaragua, and the Mosquitoes all claimed the mouth of the San Juan; Honduras and Nicaragua, the control of the Pacific outlet. British diplomatic and naval officers clashed with those of the United States until, in their search for complete control, both exceeded the instructions which they had received from home. The British occupied Greytown on the San Juan and supported the Mosquitoes and Costa Rica. The Americans won favor in Nicaragua and Honduras, framed treaties allowing transit and canal construction, and proposed the annexation of Tigre Island, which, commanded the proposed Pacific outlet.