When King Kamehameha stationed his troops on the beaches of Waikīkī in preparation for the battle to take O‘ahu, he stationed lookouts at Pu‘u O Kaimukī (aka “Kaimukī Hill”) to spot enemies arriving by sea.
When Honolulu became a major port, “Kaimukī Hill” was used as a signal station (using semaphore technology,) giving it the name “telegraph hill.” It had broad view over the Pacific and line-of-sight to downtown Honolulu. Back then, they used this vantage point to spot ships coming in, and then conveyed the news to Honolulu.
Optical “telegraphs” or signaling devices have been traced back to ancient times (initially using torches) and were the fastest systems to convey messages over long distances; these “telegraphs” eventually moved toward semaphore towers.
If Internet and its communications channels are at the forefront of the signaling opportunities of the 21st century, the semaphore was the signals intelligence breakthrough at the time of Napoleon (and Washington and Kamehameha.)
Semaphore towers used arms and blades/paddles to convey messages; messages were conveyed/decoded based on the fixed positions of these arms.
During the Napoleonic Wars, the French revolutionized land-based communications with the construction of semaphore towers bearing rotating arms to fashion coded signals. The British quickly followed suit in that new era of signals intelligence.
The semaphore tower/semaphore line design was first thought up by Robert Hooke in 1684 and submitted to the Royal Society. The system was not implemented, though, due to military concerns.
However, this did lead to Claude Chappe developing the first visual telegraph in 1792 – eventually covering much of France via 556 stations. In France, this was the primary source of communication for military and national applications, until it became more widely used in the 1850s.
In Hawaiʻi, Kaimukī Hill had been used as a semaphore signal station ever since Fair Haven (Honolulu Harbor) became prominent in Hawaiian commerce. This semaphore station reported all incoming ships from Koko Head to Barber’s Point.
“Before the telephone was invented, and long before the system was in use in Honolulu, we had the lookout station on Telegraph Hill, which by means of a semaphore arrangement communicated with a station on the building (downtown.) Every merchant was supplied with the code, and whenever a schooner, a steamer, a mail packet, or a man of war, was sighted, the heart of the town knew it immediately.” (Hawaiian Star, February 10, 1899)
“From Telegraph Hill and the slopes toward Waiʻalae may be seen Koko Head, the beautiful expanse of ocean and on clear days the distant islands of Molokai, Lanai, and Maui. On the town side, the residents look over the town, across the cane fields to the Waianae range.” (Evening Bulletin, September 26, 1898)
“Mauka of Diamond Head, for a distance of three or four miles is a high ridge that vernacular geologists call a “hog back.” At the most elevated point on this ridge is the debris of Telegraph Hill (Kaimuki). In the olden days vessels coming from the north were signalled to the city from Kaimuki by a semaphore system, clear and effective. The town end of the line was a building on Kaahumanu street, then occupied as a sail loft.” (Hawaiian Gazette, January 13, 1899)
Reportedly, in 1857, a semaphore mechanism on Puʻu O Kaimukī, with large moveable arms, was attached to the top of a sixty-foot pole and used to signal to Honolulu.
The official receiving station from Kaimukī was on Merchant Street, but some have suggested other receiving stations at Kaʻahumanu Street and the foot of Nuʻuanu.
Upon receiving the message, a signal was broadcast to the town noting the names and ports of origin of each ship coming into view. This information was announced in Honolulu by loud proclamation and bell ringing, and preparation made to tow the vessel in by hand or bullock power.
In 1866, the roof of Honolulu Hale on Merchant Street was fitted with a new marine lookout with a taller semaphore, making its signals accessible to a larger segment of the population.
This optical telegraph system was an important tool for residents of Honolulu. The signals were unique and people became familiar with them, so most could decode the signal and know which ships were coming.
Likewise, besides alerting the postmaster to the imminent arrival of the mail, it was helpful to merchants expecting new goods and people awaiting friends and relatives.
Semaphore was then called “marine telegraph”, and it seems logical that the early map-makers of Hawaiʻi would name the hill “Telegraph Hill.”
“When the telephone system got into working order the lookout station was moved to a position on Diamond Head which gave a view further along the channel, because it was no longer necessary for the station to be in full view of the city.” (Hawaiian Star, February 10, 1899)
Puʻu O Kaimukī had several colloquial names; one was Christmas Tree Park. There’s a bare metal Christmas-Tree-looking pole. It’s not a remnant of the prior semaphore communications, it’s just a Christmas tree, built by the City and County soon after the park’s christening in 1991. Every year since then the big metal tree gets hung with Christmas lights.
It’s also referred to as Reservoir Park, a reminder of the days in the early 1900s when the top of the hill housed a water storage tank for the Honolulu Water Works. Another name is Bunker Hill, from the World War II era when the spot became a handy surveillance bunker for the military.
It’s known today as Puʻu o Kaimukī Park and is just behind (makai) the Kaimukī Fire Station.
On November 13, 1900, the first Marconi wireless telegraph system was set up and messages were sent and received between Oʻahu and Molokaʻi across a twenty-eight mile channel. Military semaphore flag signals are still used, today