han present day Panama and Colombia combined—which by then had adopted the name of Republic of New Granada. The alliance of the two nations would last seventy years and prove precarious.
By July 1831, as the new countries of Venezuela and Ecuador were being established, the isthmus would again declare its independence, now under the same General Alzuru as supreme military commander. Abuses committed by Alzuru's shortlived administration were countered by military forces under the command of Colonel Tomás Herrera, resulting in the defeat and execution of Alzuru in August, and the reestablishment of ties with New Granada.
In November 1840, during a civil war that had begun as a religious conflict, the isthmus under the leadership of, now General, Tomás Herrera, who assumed the title of Superior Civil Chief, declared its independence as did multiple other local authorities. In March 1841, the State of Panama adopted the name 'Estado Libre del Istmo', or the Free State of the Isthmus. The new state established external political and economic ties and by March 1841, had drawn up a constitution which included the possibility for Panama to rejoin New Granada, but only as a federal district. Herrera's title was first changed to Superior Chief of State in March 1841 and in June 1841, to President. By the time the civil conflict ended and the government of New Granada along with the government of the Isthmus had negotiated the Isthmus' reincorporation to the union, Panama's First Republic had been free for 13 months. Reunification occurred on December 31, 1841.
In the 1840s, two decades after the Monroe Doctrine declared the Western Hemisphere to be in the United States sphere of influence, North American and French interests became excited about the prospects of constructing railroads and/or canals through Central America to quicken trans-oceanic travel. At the same time, it was clear that New Granada’s control over the isthmus was turning increasingly untenable. In 1846, the United States and New Granada signed the Bidlack Mallarino Treaty, granting the U.S. rights to build railroads through Panama, and—most significantly—the power to militarily intervene against revolt to guarantee New Granadine control of the isthmus. The world's first transcontinental railroad, the Panama Railway, was completed in 1855 across the Isthmus from Aspinwall/Colón to Panama City.
From 1850 until 1903, the United States used troops to suppress separatist uprisings and quell social disturbances on many occasions, creating a long-term animosity among the Panamanian people against the US military and resentment against Bogotá. The Bidlack-Mallarino Treaty would usher in a new era of U.S. intervention which would linger on into the new millennium. The first of many such conflicts was known as the Watermelon War of 1856, where U.S. soldiers mistreated locals, causing large-scale race riots that U.S. Marines eventually put down.
On November 3, 1903, Panama declared its independence from Colombia. The U.S. Battleship Nashville prevented the Colombian military from sailing to Panama. An invasion through the dense Panamanian jungle was impossible. The President of the Municipal Council, Demetrio H. Brid, highest authority at the time, became its de facto President, appointing a Provisional Government on November 4, to run the affairs of the new republic. The United States, as the first country to recognize the new Republic of Panama, sent troops to protect its economic interests. The 1904 Constituent Assembly elected Dr. Manuel Amador Guerrero, a prominent member of the Conservative political party, as the first constitutional President of the Republic of Panama.
From 1903 until 1968, Panama was a republic dominated by a commercially-oriented oligarchy. During the 1950s, the Panamanian military began to challenge the oligarchy's political hegemony. The January 9, 1964 Martyrs' Day riots escalated tensions between the country and the U.S. government over its long-term occupation of the Canal Zone. Twenty rioters were killed, and 500 other Panamanians were wou