The growth of the industry was aided by Hawaiian Kingdom legislative acts in 1848 and 1850. The earlier law allowed non-Hawaiians to own land and the later permitted contract laborers from other countries to be imported to work the fields. By war's end in 1865 there were thirty-two plantations, most with milling companies, compared to only twelve in 1860. The US-Hawaii Reciprocity Treaty in 1876, which removed tariffs on sugar shipments to the mainland, boosted the industry's viability and eventually over 60 plantations and mills dotted the Hawaiian Kingdom's landscape. The sugar barons, who cultivated their political contacts in Washington, D.C. as well as they did their sugar cane fields, eventually used their clout to entice the US government to support their overthrow of the Hawaiian Kingdom to establish an independent Republic, and eventually achieve annexation and statehood for the islands.
Sugar cane requires an abundance of both water and sunlight for maximum productivity.
The key to expanding sugar cane cultivation on Maui lay in bringing water to the island's central plain, formed by the isthmus between two volcanoes. Water from the ditch system privately developed for Maui's sugar plantation is shared by the county of Maui, providing approximately one-third of the domestic water supply. At the sugar boom's peak, Maui had eleven operational plantations and mills located from Kipahulu and Hana in the east to Lahaina in the west, and from Ulupalakua and Makawao upcountry to Wailuku in the north. King sugar's appetite for laborers was the impetus behind Hawaii's reputation as a melting pot of the Pacific Rim, although the industry's search for cheap labor was not limited to the Pacific region. They were followed by waves of workers from Japan, Portugal, Puerto Rico, Philippines and other Pacific islands.