This 1899 Government Survey Map of Oahu (courtesy of davidrumsey.com) shows Kona district, encompassing Honolulu, colored in goldenrod at the southernmost end of the island. Going clockwise, Ewa district is colored in pink, Waianae district is colored in goldenrod and Waialua district is in gray. The two northeastern facing, or windward, districts are Koolauloa, colored in pink at the north end and Koolaupoko, colored in gray, at the southeast end.
In 1856, five country post offices were opened on Oahu: Ewa, on the northern shore of Pearl Harbor in the Waiawa ahupua'a of the Ewa district, part of present day Pearl City; Waialua on the north shore of the island near the mouth of the Anahola River in the Kawailoa ahupua'a of the Waialua district, at present day Haleiwa; and three on windward Oahu (two in the Koolauloa district: Kahuku at the northern tip of the island and the other in Hauula on the central Koolauloa coast; and Kaneohe in the Koolaupoko district at the head of Kaneohe Bay). The Waianae district was left out. The offices at Hauula and Kahuku closed in 1861 but in 1865 two more offices sprang up around Kaneohe Bay: at Kahaluu and Kualoa. Kualoa was short lived – it closed by the end of 1865. Kahaluu and Kaneohe closed in 1867. In 1868, only the post offices in Ewa and Waialua districts were open. Ewa closed in 1871, leaving only Waialua on the remote north shore. A post office opened and closed at Laie (1878-1879) in Koolauloa. Thus, in 1880 the post office in Waialua once again was the only country office on Oahu.
The lack of post offices around Oahu before 1880 probably made little difference to most of the people living there. For one thing, the population was sparse. At 1878 (the nearest census date to 1880), Honolulu had a population of 14,114 people. Going clockwise around the island, Ewa and Waianae districts (central Oahu and the western coast) were counted together and had a combined population of 1,699 people, most of whom lived along the western Waianae coast or on the northern shore of Pearl Harbor; only 939 people lived in the Waialua district; Koolauloa had 1,082 people, most of whom lived in the southern part of this district just to the north of Kaneohe Bay; and Koolaupoko had 2,402 people mostly concentrated in the land districts around Kaneohe Bay. The population of the entire island of Oahu in 1878 was 20,236 with 30% of the people (6,122) living outside Honolulu. Apart from the Kaneohe Bay area, and a few settlements around Pearl Harbor and in Waianae, Oahu outside Honolulu was mostly open range land for cattle and horses.
Another factor contributing to the lack of need for an efficient postal service was the close proximity of families near Kaneohe Bay where most people in outer Oahu lived. In the early years the mostly Hawaiian population cultivated taro and bananas. Beginning in the 1850s Chinese contract laborers came to windward Oahu and eventually formed families who cultivated rice. Within the confines of the Kaneohe Bay region families relied more on personal visitations than the mail for communication.
Residents of western extraction who had more need for the mail were few, mostly scattered ranchers or plantation owners, religious missionaries or teachers affiliated with the missions and wealthy folks from Honolulu with country retreats. Commercial sugar planting would drive a population boom in outer Oahu but it was slow to start. Before 1880, only two sugar plantations of substance were formally organized: Waianae Sugar Co. (1878) on the western coast and Heeia Agricultural Company (1879) near Kaneohe Bay. Six small acreage plantations were tried in Koolaupoko: Kualoa (1864-1871), Kaalaea (1865-1883), Kahaluu (around 1879-1880), Parker Sugar Company at Kaneohe (1880), Keaahala in Kaneohe (1870s) and Kaneohe Sugar Plantation (1865-1885).
For the small mail service demand before 1880, the weekly overland carrier making the around-the-island circuit picked up or dropped letters at boxes kept by various resident volunteers at strategic locations. Around Kaneohe Bay, letter boxes were kept in Kaneohe, Heeia, Kahaluu and Kualoa. In Koolauloa, there were letter boxes at Kaaawa, Haleaha, Hauula, Laie and Kahuku. There may have been other places where the overland carrier knew to stop and check for mail. Interisland schooners began to call at more or less frequent intervals at Waianae, Waialua and several windward spots and they offered another way to transmit mail to or from Honolulu.
Beginning in 1880, sugar planting intensified on Oahu with the successful drilling of artesian wells on the arid Honouliuli Plain of west Ewa. Irrigation projects elsewhere brought water to Kahuku and other places in sufficient quantities to sustain sugar crops. Sugar plantations brought more people to outer Oahu, including more foreigners. Ewa, Waialua and Koolauloa districts grew remarkably, reflecting the success of sugar plantations there. Koolaupoko grew at a comparatively slow pace due to the abandonment of many sugar plantations there and the return to rice and taro cultivation and ranching. Waianae had little growth because its limited sugar acreage grew to near maximum cultivation before 1880. Censuses taken in each of the years 1884, 1890, 1896 and 1900 trace the growth. By 1900, Honolulu’s population had grown about 170% since 1878, from 14,114 to 39,306. In the same period, the population of Ewa district grew 470% to 9,689, Waialua grew 250% to 3,285 and Koolauloa grew 120% to 2,372. Koolaupoko grew 18% to 2,844 and Waianae grew only 10% to 1,008. At 1900, the population of Oahu was 58,504, with 33% of the people (19,198) living outside of Honolulu. Most growth consisted of foreigners brought to outer Oahu as laborers (Japanese and Portuguese) or skilled workers (Americans and northern Europeans).
Growth in outer Oahu created pressure to improve postal service. In the 1880s six offices were opened or re-opened: two in Koolaupoko at Kaneohe and Waikane/Waiahole (1881); one at Waianae (1882); two in Koolauloa at Punaluu (1883) and Laie (1889); and Ewa (1889) in present day Pearl City. Thus at the close of the 1880s, outer Oahu had seven post offices: Ewa, Waianae, Waialua, Laie, Punaluu, Waikane/Waiahole and Kaneohe. Whether there ever were two post offices open at the same time in Waikane and Waiahole is unclear. For most of the time there was just one office, sometimes located in Waiahole and sometimes in neighboring Waikane with either name used to identify the one post office. During the 1890s, there were no post office closings and additional post offices were opened at Honouliuli and Kahuku (1890), Heeia (1891), Peninsula and Waipahu (1897) and Aiea, Hauula, Wahiawa, Waialua Plantation and Waimanalo (1899). In 1900, 17 post offices were operating on Oahu outside Honolulu. Letter drops where the overland carrier could pick up mail existed in places not served by a post office.
Interisland steamships began scheduled (albeit unreliable) semi-weekly service to Waianae and Waialua in 1884. During the late 1880s and 1890s, steamships were scheduled for regular visits along the windward coast. The steamships offered an alternative way to send mail to or from Honolulu. In the 1890s the Oahu Railroad was built, finally reaching Kahuku at the northern point of the island in 1899, going via Aiea, Pearl City, Ewa, Waipahu, Honouliuli, Waianae and Waialua. As the rail reached various towns along its route, the train became the main way to transmit mail to or from Honolulu.