Colón, city (1990 pop. 140,908), Panama, at the Caribbean end of the Panama Canal. Colón, the second largest city in Panama, was surrounded by, but not part of, the former Panama Canal Zone. Colón is an important port, commercial center, and tourist destination. It was made a free trade zone in 1953 and is the world's second largest duty-free port (the principal tourist attraction). The city was founded in 1850 by Americans working on the trans-Panama railroad and was named Aspinwall until 1890. Built on a swampy island, the city was often scourged by yellow fever until the sanitary work associated with the construction of the canal was completed under W. C. Gorgas.