The Panama Crisis of 1885 was an intervention by the United States in a rebellion in Panama, then part of Colombia, and the ensuing show of force made by Chile.
In 1846, the Mallarino–Bidlack Treaty was signed by the Republic of New Granada (Colombia and Panama) and the United States, obligating the United States to maintain "neutrality" in the Colombian state of Panama in exchange for transit rights in the isthmus on behalf of Colombia.
Chile's influence in the region followed its victory in the War of the Pacific. During the war, Chile had defeated Bolivia and Peru and gained large swathes of territory from both, removing Bolivia's access to the sea. U.S. sympathies were with Bolivia and Peru, and Chile rejected American attempts at mediation. A Peruvian attempt to cede a naval base to the U.S. in Chimbote Bay in 1881 was blocked when Chile, learning of the deal, sent marines to occupy Chimbote.
In March 1885 Colombia thinned its military presence in Panama by sending troops stationed there to fight rebels in Cartagena. These favourable conditions prompted an insurgency in Panama. The United States Navy was sent there to keep order, in light of invoking its obligations according to the treaty being signed in 1846.
On 7 April, the screw sloop USS Shenandoah arrived in Panama City and three days later, other American ships started arriving in Colón, Panama. On 27 April a force of marines was landed in Panama City to help suppress rebels who had taken over the city when local troops had moved out to deal with a revolt in Colón. The next day, federal troops from Colombia arrived from Buenaventura, Colombia's nearest Pacific port. By this time, there was also a small force of the National Army of Colombia supported by a strong contingent of American troops in Colón.