Hilo, Hawaii
A breakwater across Hilo Bay was begun in the 1900s and completed in 1929. On April 1, 1946, a 7.8 magnitude earthquake near the Aleutian Islands created a fourteen-meter high tsunami that hit Hilo 4.9 hours later, killing 160 people. In response an early warning system, the Pacific Tsunami Warning Center, was established in 1949 to track these killer waves and provide warning.  This tsunami also meant the end of the Hawaii Consolidated Railway, and instead the Hawaii Belt Road was built north of Hilo using some of the railbed.