Diamond Head Lighthouse stands beside a tuff-cone volcano formed by explosive eruptions thousands of years ago. In 1825, British sailors climbed the crater and found hard, clear calcite crystals among the black rocks, mistook them for diamonds, and gave the crater the name Diamond Head. One Hawaiian name for Diamond Head is “leahi,” meaning “wreath of fire,” reflecting the ancient Hawaiian practice of lighting a fire on the volcano’s crest to guide canoe fleets back to the island. The first lighthouse at this site was built in 1899 and was rebuilt in 1917 after cracks developed in the earlier structure. It still uses the original Fresnell Lens, which focuses the flash of a modern 1000-watt electric bulb so it can be seen more than 18 miles out to sea. In 1939, the Lighthouse Service was combined with the Coast Guard, which since then has maintained lighthouses, buoys, and other aids to navigation throughout the United States. The lighthouse keeper’s dwelling, built in 1921, now serves as the quarters of the Commander, Fourteenth Coast Guard District.