Canal this trend. Yet in other countries canals grew in size as construction techniques improved. During the 19th century in the US, the length of canals grew from to over 4,000, with a complex network making the Great Lakes navigable, in conjunction with Canada, although some canals were later drained and used as railroad rights-of-way. In the United States, navigable canals reached into isolated areas and brought them in touch with the world beyond. By 1825 the Erie Canal, long with 36 locks, opened up a connection from the populated Northeast to the Great Lakes. Settlers flooded into regions serviced by
Asian carp introduced. The United States Environmental Protection Agency is also concerned about the possibility of Asian carp migrating to the Great Lakes. In 2002, the U.S. Army Corps of Engineers completed an electric fish barrier in the Chicago Sanitary and Ship Canal, the only navigable aquatic link between the Great Lakes and the Mississippi River drainage basins. The initial fish barrier was used as a demonstration project to study the design's effectiveness. Following positive results, construction began on a second, permanent barrier in 2004. In addition to the canal, the corps has identified 19 sites in five additional states, from Minnesota