The construction of Lock and Dam 19 obliterated the Des Moines rapids, effectively the northern barrier to traffic on the Mississippi. The dam is 4,620 feet long and consists of 119 30-foot sliding gates. It was the second longest dam in the world when it was completed. It is also a hydroelectric dam, and when finished in 1913 the powerhouse was the largest in the world. The lock and powerhouse are located on the Iowa side.