Before satellites, a ship at sea was on its own unless it could reach a coast station — a shore-based radio station that carried its telegrams, its weather, its phone calls home, and, when things went wrong, its call for help. For most of the twentieth century the marine bands were packed end to end with these stations, each with its own call sign and its own slice of ocean, the skilled operators trading Morse around the clock. This page is a guide to the American ones: the great commercial Morse and radiotelephone stations, the Coast Guard network that outlived them all, and the stations of Alaska, Hawaii, Guam, Puerto Rico, and the Virgin Islands. Most are silent now. A few are still keying. It's a companion to the U.S. shortwave broadcasters and time stations pages.
Noncommercial hobby compilation, gathered from public sources including the Maritime Radio Historical Society, the U.S. Coast Guard Navigation Center, and naval-radio history archives. Corrections welcome — chris@n6jet.com.
In scope: coast stations of the United States and its territories — the privately operated commercial stations (RCA, Mackay/ITT, Press Wireless, Globe Wireless, AT&T) and the government stations (U.S. Navy and Coast Guard) — across the mainland, Alaska, Hawaii, Guam, Puerto Rico, and the U.S. Virgin Islands. Both on-air and long-silent stations are included.
Not here: Canadian and Mexican coast stations (a story for another page), and the broadcast and time-and-frequency stations covered on the companion pages above.
How they worked — from spark to digital
The voice years — AT&T High Seas
WLO: the last commercial survivor
KPH and KFS: the stations that came back
The commercial, AT&T High Seas, and Coast Guard stations on this page, by location — those still keying and those long silent alike. Mainland sites are shown in place; the off-continent territorial stations appear in the strip below.
Locations are approximate transmitter/site positions for orientation, not precise coordinates. Several West Coast calls (KPH, KMI, NMC) share the Point Reyes area and are plotted close together.
A coast station is the shore end of a ship-to-shore radio link. A vessel's radio officer would call the nearest station on a shared calling channel, the two would agree to shift to a working channel, and there the station would pass traffic: commercial telegrams (“radiograms”), personal messages, position reports, weather, and later telephone calls patched into the landline network. Just as important, the station kept a continuous listening watch on the distress frequencies, ready to answer a ship in trouble and summon help.
In the golden age the globe held hundreds of these stations standing shoulder to shoulder across the bands. In the United States they fell into two broad camps. The commercial stations — run by companies like RCA, Mackay, and AT&T — handled paid traffic for merchant ships and existed to make money. The government stations — Navy and Coast Guard — existed for safety and defense, but were opened to public ship-to-shore service as early as 1913, which made them the coastal radio backbone in places the commercial firms never bothered to wire, especially the Pacific and Caribbean territories.
The modulation arc of the coast stations runs straight through the history of radio itself, and it touches AM at nearly every step.
Spark, then CW Morse. The earliest stations radiated damped-wave spark — raw, broad, and noisy — before settling into clean continuous-wave Morse: on-off keying of a steady carrier, the dits and dahs that defined the profession. The anchor was 500 kHz (“600 meters”), the international calling and distress channel, where every station kept watch and observed the twice-hourly silence periods.
AM radiotelephone. When voice came to the marine bands it arrived as amplitude modulation — ordinary AM, the same mode as a broadcast station — on medium- and high-frequency channels. The medium-frequency voice distress and calling frequency, 2182 kHz, began life in AM and double-sideband before the service moved to single sideband; some older sets and coast stations stayed compatible with plain AM well into the SSB era. Single sideband (SSB) is simply AM with the carrier and one sideband stripped away to save power and spectrum, and by the 1970s it had become the standard for marine voice.
Radioteletype, then digital. From the 1930s onward Morse was joined by radioteletype (RTTY), and later by the marine telex modes SITOR and PACTOR, which carried error-corrected text and, eventually, email by radio. Today the whole edifice has been replaced by the Global Maritime Distress and Safety System (GMDSS): digital selective calling (DSC), NAVTEX, satellite EPIRBs, and synthesized-voice weather. The carrier still carries the message — it's just a data burst now instead of a fist on a key.
For most of a century, 500 kilohertz was the most important frequency on Earth for a sailor. It was the international Morse calling and distress channel, and the place an SOS would be heard. To protect weak or distant calls, every station observed the silence periods: twice an hour, from h+15 to h+18 and h+45 to h+48 minutes, all routine traffic stopped and everyone simply listened. A ship's radio-room clock had those sectors shaded in red as a reminder. (The voice frequency 2182 kHz had its own green-shaded silence periods at h+00 and h+30.) The watch on 500 kHz faded with Morse itself in the 1990s, and under GMDSS the silence periods are no longer required — but ask any old radio officer and the number still means something.
The paid-traffic stations were run by a handful of companies — RCA (the old Marconi inheritance), Mackay Radio & Telegraph / ITT, Press Wireless, and later Globe Wireless, which consolidated many of the famous calls and ran HF radio-email until it sunset its high-frequency network around 2013–14. Almost all of these stations did business in Morse, anchored on 500 kHz and the HF marine bands, with radioteletex layered on later.
| Call | Location | Operator | Story & fate |
|---|---|---|---|
| WCC | Chatham / Marion, MA | RCA (orig. Marconi) | Built by Marconi in 1914, sold to RCA in 1920, and the busiest coast station in the U.S. public ship-to-shore service for most of the century. Now the Chatham Marconi Maritime Center museum, with ham station WA1WCC on site. |
| WSL | Sayville / Amagansett, Long Island, NY | Mackay / ITT | A flagship East Coast Morse station. The transmitter site at Napeague now belongs to New York State; its towers had been a charted navigation checkpoint. |
| WSC | Tuckerton, NJ | Mackay | One of the northeastern Morse stations; long silent. |
| WSE | Sea Gate, Brooklyn, NY | commercial | A New York harbor-area coast station of the early-to-mid century. |
| WNU | Slidell, LA | Mackay Radio | The major Gulf of Mexico Morse station, covering the oil-and-shipping traffic of the Gulf. Later a Globe Wireless call; now silent. |
| KLC | Galveston, TX | commercial | A Texas Gulf coast station serving the western Gulf. |
| WPD | Tampa, FL | commercial | A Florida Gulf-coast Morse station. |
| KPH | Bolinas / Point Reyes, CA | RCA | The “wireless giant of the Pacific.” Began at the Palace Hotel in San Francisco as “PH”; relocated to Marin County under RCA. Ended commercial service in 1997 — revived as a heritage station (see below). |
| KFS | Half Moon Bay / Palo Alto, CA | Poulsen / Mackay / Globe | Began at Ocean Beach, San Francisco in 1910 under Poulsen Wireless; the Half Moon Bay receive site was built by Mackay in 1932; later run as Globe Wireless. Sent the last official commercial Morse transmission in America on July 12, 1999 — commemorated every year as “Night of Nights.” Globe was absorbed by Inmarsat in 2013; the commercial KFS license is now held by Global HFNet LLC, while the call lives on through the MRHS heritage operation. |
| KOK | Los Angeles, CA | RCA | The Southern California RCA marine station; long gone from commercial service. |
Telephone calls were a different business, and a different company. AT&T ran the “High Seas” marine radiotelephone service — voice, not Morse — that let a passenger or crew member place an actual phone call from mid-ocean, patched through to the landline network. There were three U.S. stations, and ship-to-shore telephone calls were handled here rather than by the Morse stations like KPH.
| Call | Location | Service | Fate |
|---|---|---|---|
| KMI | Point Reyes / Dixon, CA | West Coast radiotelephone (AM, later SSB) | The Pacific High Seas station, near — but separate from — the Morse giant KPH. |
| WOM | Fort Lauderdale, FL | Southeast / Gulf radiotelephone | The Florida High Seas station. |
| WOO | Ocean Gate, NJ | East Coast radiotelephone | The Atlantic High Seas station. |
From an ordinary American telephone, you reached a ship by dialing 1-800-HIGH-SEA(S). The final S was the twelfth digit — one more than the switch actually needed — so the central office simply ignored it. The number worked whether you dialed the last letter or not. Somebody at AT&T knew exactly what they were doing.
The call landed with a High Seas operator at the International Operating Center in Pittsburgh, who took the ship's name, the name of the person being called, and the caller's number. The operator then telephoned whichever coast station could reach that patch of ocean — WOO, WOM, or KMI — and the station called the ship.
It was not a connection so much as a relay of humans, and it worked for the better part of fifty years.
All three went silent around 1999, when Inmarsat satellite telephony made HF radiotelephone obsolete almost overnight. With them ended the era of placing a ship-to-shore phone call by riding the ionosphere.
One American commercial HF marine station is still standing. WLO, on the Gulf coast at Mobile, Alabama, was founded in 1947 as Mobile Marine Radio and grew into the country's full-service provider of voice, data, and email to ships at sea — it pioneered radiotelex at sea and was the first U.S. coastal station to offer it. Operated today by ShipCom LLC (with a Pacific-coast partner station, KLB, near Seattle), WLO went quiet around 2018 but came back: its FCC license was renewed effective April 2023 and runs to 2031, and it's once again on the air — notably on 8788 kHz upper sideband — with automated marine weather broadcasts and its distinctive SELCAL tones. It's a fraction of the old “flamethrower” that could be heard on a piece of wire — today largely automated — but ShipCom remains the last commercial high-seas marine operator in the United States, running WLO on the Gulf and its Pacific sister KLB.
When KPH's Bolinas/Point Reyes site went dark in 1997, two former operators found it not vandalized but intact — a radio time capsule, receivers still warm. They formed the Maritime Radio Historical Society (MRHS), convinced the National Park Service (the site sits within Point Reyes National Seashore), and put it all back on the air. Today the MRHS keys KPH, the old Mackay/Globe call KFS, and the club station K6KPH from the original 1914 Marconi transmitter site at Bolinas, with the 1930 RCA receive station at Point Reyes — every Saturday, in real Morse, working ships and amateurs. They even hold a backup coast-station license, KSM, granted when nobody had applied for a new Morse coast station in forty years.
Once a year, on July 12 (0001 UTC July 13) — the anniversary of KFS's 1999 farewell — they hold “Night of Nights,” when KPH, KFS, and K6KPH pour Morse back onto the shortwave and medium-wave bands and a rotating cast of other historic stations checks in. For listeners, the MRHS even runs KiwiSDR receivers at the Point Reyes site so you can hear both the coast station and the ships answering it.
The stations that outlived all the commercial operators are the U.S. Coast Guard's — the “NM-” calls. The first Coast Guard shore station was established after 1924 at Rockaway Point (Fort Tilden, New York), and the network grew through the 1930s along both coasts. Automation later drove a sweeping consolidation under the master-station concept: a single station now staffs and remotely keys the others. NMN took over Washington's duties in 1976, then absorbed remote operation of Miami in 1993, Boston in 1996, and New Orleans in 1998.
The modern high-seas network, organized around two master stations and centrally run from Communications Command (COMMCOM) at Chesapeake, Virginia:
| Call | Station | Role |
|---|---|---|
| NMN | CAMSLANT / COMMCOM Chesapeake, VA | The Atlantic master station, covering Maine to Brownsville and out to sea — and the control point that remotely keys the other Atlantic and Gulf stations. |
| NMF | COMMSTA Boston, MA | New England transmit site; also broadcasts International Ice Patrol charts. |
| NMA | COMMSTA Miami, FL | Southeast / Caribbean transmit site. |
| NMG | COMMSTA New Orleans, LA | Gulf of Mexico transmit site. |
| NME | Charleston / Savannah, SC | NAVTEX transmitter site. |
| NMC | CAMSPAC Point Reyes, CA | The Pacific master station, remotely keying Honolulu and Guam. |
| NMO | COMMSTA Honolulu, HI | Central-Pacific transmit site (Wahiawa, Oahu). |
| NRV | COMMSTA Guam | Western-Pacific transmit site. |
| NOJ | COMMSTA Kodiak, AK | The Alaska station — and the one still staffed and watch-kept locally. |
The Morse is long gone; what the Coast Guard transmits now is NAVTEX on 518 kHz, radiofax weather charts, SITOR text, and single-sideband voice. The high-seas forecasts and storm warnings go out in a synthesized voice nicknamed “Iron Mike” — distinctive enough that listeners use it to identify the broadcast. NMF Boston, for the record, is the station that answered the Marine Electric's SOS.
The distress watch has narrowed in stages, and it's worth being precise about what survives: the 500 kHz Morse watch ended with Morse itself in the 1990s; the medium-frequency voice watch on 2182 kHz (with DSC 2187.5 kHz and broadcasts on 2670 kHz) was terminated on August 1, 2013; and HF voice distress watch in the contiguous U.S. and Hawaii ended on February 7, 2022. What the Coast Guard still guards is HF digital selective calling — the DSC distress channels at 4207.5, 6312, 8414.5, 12577, and 16804.5 kHz — where a vessel's distress button sends a digital burst with its GPS position, watched automatically by NMN, NMC, NMF, NMA, and NMG. So NMC Point Reyes is still on the air and still on distress duty; it simply listens for data now, not a human voice.
Out in the territories, the coastal-radio story belongs mostly to the Navy and Coast Guard. The Navy built the early station chains between roughly 1903 and 1914 — along the coasts, through the West Indies and Panama, and across the Pacific to Hawaii, Guam, Samoa, and the Philippines — and opened them to public ship-to-shore traffic in 1913. Commercial firms (RCA, Press Wireless, Globe Wireless) layered in later, mostly for point-to-point and a little maritime work.
NMO — Coast Guard Radio Honolulu, at Wahiawa on Oahu — was the central-Pacific ship-to-shore hub, with operating positions for 500 kc CW, HF CW, voice, RTTY and Fleet Broadcast, and the longest over-water microwave link in the world (Oahu to Kauai). The Navy's Hawaii station, NPM, goes back to the Wailupe and Haiku Valley Alexanderson-alternator days and today survives as the Lualualei VLF transmitter, talking to submerged submarines on 21.4 and 23.4 kHz. The first Hawaiian wireless was commercial and inter-island: the Mutual Telephone Company ran stations under the calls KHK, KHL, KHM, KHN, and KHO from 1900, and RCA's Kahuku station and Press Wireless's KDG handled transpacific point-to-point.
Guam carried a remarkable cluster: NPN (U.S. Navy, at Barrigada near Agana) and NRV (U.S. Coast Guard, built on Cabras Island in Apra Harbor in 1944, its Morse dropped on April 1, 1995 when operations were remoted to Hawaii and Point Reyes). On the commercial side, RCA installed point-to-point station KUJ/KUK after the Pacific War — beaming San Francisco with a 730-foot rhombic — and Globe Wireless later ran a low-power maritime station, KHF, from Yona and Talofofo until Globe shut down.
Alaska's modern anchor is NOJ, Coast Guard Communication Station Kodiak — the one high-seas station still keeping its own local watch, covering the Gulf of Alaska and Bering Sea. The Navy's early Pacific chain reached north to Kodiak, Sitka, Dutch Harbor, Unalga, and St. Paul in the Pribilofs, and commercial and fishery stations such as WKR at Nome and the Alaska fisheries stations served the coastal and cannery trade.
The first wireless station in Puerto Rico was the Navy's NAU at San Juan: in December 1903 a three-kilowatt transmitter was installed to work a sister station on Culebra Island and ships on the high seas, and a larger station followed in the 1905 buildout. The Coast Guard later carried San Juan forward as NMR. In the Virgin Islands, the Navy ran stations at St. Thomas (NBB) and St. Croix (NNI). (For the record, the early Navy station at Guantanamo Bay, Cuba, was NAW — pre-1945 and U.S.-operated, though Cuba itself is beyond this page's scope.)
The golden age is over, but the bands aren't entirely silent. WLO in Mobile hangs on as the last commercial high-seas station. KPH and KFS live again as heritage stations every Saturday and on Night of Nights, kept alive by the volunteers of the MRHS. And underneath it all the Coast Guard's NM-stations — NMN, NMC, NMF, NMA, NMG, NMO, NRV, and NOJ — keep the actual watch, pouring weather onto the HF bands and guarding the digital distress channels around the clock, in SSB and DSC now instead of dits and dahs. The relics, too, are preserved: the Chatham Marconi Maritime Center where WCC once roared, the WSL towers on Long Island, and the original KPH gear still warm at Point Reyes.
From spark to Morse to AM voice to single sideband to a silent digital guard — the American coast stations carried a century of the maritime world's messages, and the steady carrier that did the carrying was, more often than not, plain amplitude modulation.
Companion pages: Shortwave from America: U.S. International Broadcast Stations · Time Stations: Standard-Frequency and Time-Signal Radio · AM Broadcast Band trivia.
Sources: the Maritime Radio Historical Society, the U.S. Coast Guard Navigation Center, Wikipedia, naval-radio history archives (navy-radio.com, jproc.ca), and standard maritime-radio references. Compiled by N6JET as a noncommercial hobby reference. Questions or corrections? Email chris@n6jet.com.