proposals were made throughout the 16th and 17th centuries, they came to naught. The late 18th and early 19th centuries saw a number of canals built. The success of the Erie Canal in the United States and the collapse of the Spanish Empire in Latin America led to a surge of American interest in building an interoceanic canal. Beginning in 1826, US officials began negotiations with Gran Colombia (present-day Colombia, Venezuela, Ecuador and Panama), hoping to gain a concession for the building of a canal. Jealous of their newly obtained independence and fearing that they would be dominated by an American presence, the president Simón Bolívar and New Granadan officials declined American offers. The new nation was politically unstable, and Panama rebelled several times during the 19th century. In 1836 U.S. statesman Charles Biddle reached an agreement with the New Granadan government to replace the old road with an improved one or a railroad, running from Panama City on the Pacific coast to the Chagres River, where a steamship service would allow passengers and freight to continue to Colón. His agreement was repudiated by the Jackson administration, which wanted rights to build a canal. In 1841, with Panama in rebellion again, British interests secured a right of way over the isthmus from the insurgent regime and occupied Nicaraguan ports that might have served as the Atlantic terminus of a canal. In 1846 the new US envoy to Bogotá, Benjamin Bidlack, was surprised when, soon after his arrival, the New Granadans proposed that the United States be the guarantor of the neutrality of the isthmus. The resulting Mallarino–Bidlack Treaty allowed the United States to intervene militarily to ensure that the interoceanic road (and when it was built, the Panama Railroad as well) would not be disrupted. New Granada hoped that other nations would sign similar treaties, but the one with the United States, which was ratified by the US Senate in June 1848 after considerable lobbying by New Granada, was the only one. The treaty led the U.S. government to contract for steamship service to Panama from ports on both coasts. When the California Gold Rush began in 1848, traffic through Panama greatly increased, and New Granada agreed to allow the Panama Railroad to be constructed by American interests. This first "transcontinental railroad" opened in 1850. There were riots in Panama City in 1856; several Americans were killed. US warships landed