In 1778, Captain James Cook arrived at Waimea Bay, the first European known to have reached the Hawaiian islands, which he named after his patron the Earl of Sandwich.[12]
During the reign of King Kamehameha, the islands of Kauaʻi and Niʻihau were the last Hawaiian Islands to join his Kingdom of Hawaiʻi. Their ruler, Kaumualiʻi, resisted Kamehameha for years. King Kamehameha twice prepared a huge armada of ships and canoes to take the islands by force, and twice failed; once due to a storm, and once due to an epidemic. In the face of the threat of a further invasion, however, Kaumualiʻi decided to join the kingdom without bloodshed, and became Kamehameha's vassal in 1810, ceding the island to the Kingdom of Hawaiʻi upon his death in 1824.[12]
In 1815-17, Kaumualiʻi led secret negotiations with representatives of the Russian-American Company in an attempt to gain Russia's military support against Kamehameha; however, the negotiations folded and the Russians were forced to abandon all of their presence in Kauaʻi, including Fort Elizabeth, after it was revealed that they did not have the support of Tsar Alexander I.
In 1835, Old Koloa Town opened a sugar mill.[12] From 1906 to 1934 the office of County Clerk was held by John Mahiʻai Kāneakua who had been active in attempts to restore Queen Liliuokalani to the throne.[13]