---
title: "First Transatlantic Telegraph Cable"
year: 1866
canonical: "https://recap.at/1866/first-transatlantic-telegraph-cable"
slug: "first-transatlantic-telegraph-cable"
recapType: "global_event"
startDate: "1866-01-01"
---

# First Transatlantic Telegraph Cable

In 1866, the SS Great Eastern successfully laid a submarine telegraph cable across the Atlantic Ocean, connecting Ireland to Newfoundland. After a failed attempt in 1858 and years of technical refinement, this cable finally enabled reliable transatlantic telegraph communication, shrinking the effective distance between Europe and North America from weeks to minutes.

## Summary

By 1866, the dream of instant transatlantic communication had already cost fortunes and claimed reputations. The first attempt in 1858, backed by Cyrus Field and financed by wealthy investors on both sides of the Atlantic, technically worked—messages crossed from Ireland to Newfoundland in August. But the cable failed within weeks, leaving Field's reputation in tatters and investors deeply skeptical about pouring more money into what looked like an elaborate con. The American Civil War then consumed attention and capital for the next several years.

Field refused to quit. After the war ended in 1865, he assembled another expedition with a stronger cable design and the massive ship Great Eastern, the largest vessel afloat at the time. On July 27, 1866, after weeks of laying cable from Valentia Island in Ireland toward Heart's Content, Newfoundland, the connection held. Telegraph operators on both continents exchanged signals that stayed stable. Unlike 1858, this wasn't a brief flicker—the cable worked, and kept working.

The engineering breakthrough came down to better materials and a more robust design. The 1858 cable, now known to have failed partly due to overvoltage from impatient operators trying to force signals through, had been abandoned in the Atlantic. The new cable used gutta-percha insulation and a thicker copper conductor, lessons written in that underwater wreckage. The Great Eastern itself was the only ship with the capacity to carry 2,500 nautical miles of cable without buckling under its own weight.

The cable's arrival in Newfoundland triggered celebrations that mixed genuine euphoria with unbridled commercial speculation. Newspapers printed headlines about the death of distance. Stock prices moved. Business interests suddenly saw real opportunity instead of Field's obsession. Within a year, a second cable was also successfully laid, providing redundancy and cementing transatlantic telegraph service as permanent infrastructure.

What 1858 had promised but failed to deliver, 1866 finally achieved: reliable, continuous communication across the ocean. Field got his vindication. The cable remained the dominant transatlantic communication method for decades, until wireless and then undersea telephone cables eventually replaced it. But for a moment in the summer of 1866, the Atlantic stopped being a barrier and became a conduit.

## Key facts

- **Cable length**: 2,625 nautical miles
- **Cable diameter**: 0.73 inches (18.5 mm)
- **Ship used**: SS Great Eastern
- **Starting point**: Valentia Island, County Kerry, Ireland
- **Landing point**: Heart's Content, Newfoundland
- **Total cable weight**: 3,000 tons
- **Previous failed attempt**: 1858
- **Chief engineer**: William Thomson (later Lord Kelvin)

## Timeline

- **1858-08-16** — First transatlantic cable fails
  The initial telegraph cable, laid aboard HMS Agamemnon and USS Niagara, operates for about three weeks before breaking down irreparably. The cable's insulation proves inadequate for sustained use.
- **1864-01-01** — Telegraph Construction and Maintenance Company incorporated
  This company, led by John Pender, is founded to manufacture and lay improved submarine cables. It begins development of a more robust cable design.
- **1866-06-30** — SS Great Eastern departs Ireland
  The massive ship, carrying 2,625 nautical miles of cable, leaves Valentia Island in County Kerry under the command of Captain Robert Halpin. The expedition includes William Thomson and other leading telegraph engineers.
- **1866-07-27** — Cable successfully lands in Newfoundland
  After 27 days at sea, the SS Great Eastern arrives at Heart's Content, Newfoundland, and successfully completes the cable connection. The first confirmed message transmitted is from Ireland to Newfoundland.
- **1866-07-28** — Official communication begins
  The transatlantic telegraph cable officially opens for commercial traffic. Messages between Europe and North America can now be transmitted in minutes rather than weeks.
- **1866-09-08** — Repair expedition returns to replace 1858 cable
  The SS Great Eastern, after successful completion of the main cable, retrieves and relays the broken 1858 cable, establishing a second transatlantic telegraph connection.

## Relationships

- **evolved into**: transatlantic-telegraph-cable — The 1858 cable succeeded after failures; the 1866 cable used improved gutta-percha insulation and stronger wire, enabling reliable transatlantic telegraph service where the earlier attempt had failed within weeks.
- **evolved into**: first-transatlantic-broadcast — Marconi's 1906 wireless broadcast built on decades of telegraph infrastructure and experience; the 1866 cable proved transatlantic communication was commercially viable, spurring investment in successor technologies.
- **happened during**: first-transatlantic-nonstop-flight — The 1866 telegraph cable was operational during the 1919 Alcock and Brown flight; the cable had already transformed transatlantic communication, providing navigation and weather data that supported aviation efforts.

## Consequences

- **1870 — Rapid expansion of transatlantic telegraph network**: By 1870, multiple competing transatlantic cables were operational, reducing transmission costs and increasing reliability. Cable companies proliferated and undersea telegraphy became a standard infrastructure investment.
- **1880 — Synchronization of international financial markets**: Stock exchanges in London, New York, and other financial centers began operating on near-synchronized timescales. Arbitrage and coordinated trading became possible within minutes rather than weeks, fundamentally altering capital flows.
- **1890 — Emergence of news wire services**: Reuters, Associated Press, and other wire services scaled operations globally on the back of transatlantic cable infrastructure. Breaking news could cross the Atlantic in minutes, reshaping journalism and public information distribution.
- **1900 — Strategic military and diplomatic integration**: Governments integrated cable-based real-time communication into military and foreign service protocols. The British Empire and other powers consolidated control over far-flung territories through instantaneous orders.
- **1914 — Submarine cable infrastructure becomes geopolitical asset**: By World War I, control of transatlantic cable networks was recognized as a critical military and intelligence advantage. Britain's dominance of cable infrastructure became a lever of soft power and wartime espionage.

## Impact

The 1866 completion of the First Transatlantic Telegraph Cable created the first instantaneous communication link between North America and Europe, collapsing what had been a two-week ocean crossing into a near-instantaneous electrical pulse. This single cable—after years of failed attempts and massive financial risk—rewired global commerce, diplomacy, and the coordination of markets across continents.

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Canonical: https://recap.at/1866/first-transatlantic-telegraph-cable