100 years ago, The Locks and Ship Canal were built by Seattle and the Corps of Engineers as a commercial navigation route.
Today the Hiram M. Chittenden (aka Ballard) Locks are the Nation's busiest with nearly 50,000 vessels/yr. "locking through". Boats can lock thru 24 hours/day, except during maintenance.
No fees are charged for visitors, commercial ships or private boats. Even guided tours and summer concerts are free.