The Içá or Putumayo River is one of the tributaries of the Amazon River, west of and parallel to the Yapura. It forms part of Colombia's border with Ecuador, as well as most of the frontier with Peru. Known as the Putumayo in the former three nations, it is called the Içá when it crosses into Brazil. Today the river is a major transport route. Almost the entire length of the river is navigated by boats. Cattle farming, along with the rubber trade, is also a major industry on the banks of the Içá. Rubber and balatá (a substance very much like gutta-percha, to the point where it is often called gutta-balatá) from the Içá area are shipped to Manaus, Brazil.
In the late 19th century, the Içá was navigated by the French explorer Jules Crevaux (1847-1882). He ascended it in a steamer drawing 6 feet (1.8 m) of water, and running day and night. He reached Cuembí, 800 miles (1,300 km) above its mouth, without finding a single rapid. Cuembí is only 200 miles (320 km) from the Pacific Ocean, in a straight line, passing through the town of Pasto in southern Colombia. Creveaux discovered the river sediments to be free of rock to the base of the Andes; the river banks were of argillaceous earth and the bottom of fine sand.