Hawaii's longest reigning monarch, Kamehameha III came to the throne when he was only nine. He shared his rule initially with Ka`ahumanu, then his half-sister Kinau who succeeded Ka`ahumanu as kuhina nui. Following a period of rebellion, Kamehameha III settled into his role and worked diligently to formalize Hawaiian government. Advised by foreigners and recognizing Western forms as a useful model, Kamehameha III established a declaration of rights, Hawaii's first constitution (1840)
, judicial and executive branches of government, and a system of land ownership under the Mahele of 1848
Despite its own political and structural growth, Hawai`i remained in a vulnerable position internationally. Several threatening visits by French gunboats preceded a five-month annexation by Britain in 1843
. Annexation by the United States was also a threat, though it was not accomplished during Kamehameha III's reign. The Islands' economy, meanwhile, tended toward capitalism under the influence of foreign trade. Sandalwood declined due to depleted forests, but was replaced by the new whaling industry. As whaling waned, cattle and ranching activity grew but it was large-scale sugar cultivation that took center stage and became the powerhouse that drove the economy into the 20th century.
Kamehameha III married Kalama Hakaleleponikapakuhaili in 1837. Their two children died in infancy. Kamehameha III adopted his nephew Alexander Liholiho at birth and named him as his successor.
In a speech celebrating the return of sovereignty to the Hawaiian Kingdom in 1843
, Kamehameha III used the phrase, "Ua mau ke ea o ka `aina i ka pono (The life of the land is perpetuated in righteousness)." His words live on as the state's motto.