The Hiram M. Chittenden Locks, known locally as the Ballard Locks, are an integral part of Seattle's extensive waterways. The busiest facility of their kind in America, the Ballard Locks form the heart of the channel connecting Puget Sound's saltwater with Seattle's main freshwater lakes. When completed in 1917, the locks were second only in size to the Panama Canal and the first of their kind on the West Coast. They function primarily to maintain the lakes' levels and allow the movement of vessels between them and the sea. The Ballard Locks are among Seattle's top tourist attractions; more than one million people visit annually. They watch salmon and other fish migrate through the fish ladder, visit the botanical gardens, and watch the nonstop parade of ships—from working vessels to pleasure craft—as they rise and fall in the locks.