The Treaty of Rome, 1957: How Six Nations Built the Common Market

How the 1957 Treaty of Rome fused six nations into the European Economic Community and Euratom, founding the common market that grew into the EU.

1 September 2026 · Part of European Integration →

On the morning of March 25, 1957, delegations from six European states climbed the steps of the Capitoline Hill in Rome to sign two treaties that neither the assembled photographers nor most of the signatories themselves fully expected to reshape a continent. In the Sala degli Orazi e Curiazi of the Palazzo dei Conservatori, ministers from Belgium, France, West Germany, Italy, Luxembourg, and the Netherlands signed instruments creating the European Economic Community (EEC) and the European Atomic Energy Community (Euratom). What began as a technical arrangement to remove tariffs and coordinate nuclear research became, within a generation, the legal foundation of the European Union. The Treaty of Rome did not create a superstate, and it did not end national rivalry in Europe. It did something narrower and more durable: it bound six economies together through law, making withdrawal too costly for any of them to attempt.

From a Failed Army to a Common Market

The road to Rome began with a collapse. In August 1954, the French National Assembly refused to ratify the European Defence Community, a plan for a joint European army that would have folded a rearmed West Germany into a supranational force rather than a national one. The vote effectively killed the idea of political and military union as the next step after the 1951 Treaty of Paris, which had created the European Coal and Steel Community. For advocates of integration, the defeat was a serious setback, but not a fatal one. If defence and high politics were too sensitive to pool, economics might not be.

That calculation drove the foreign ministers of the ECSC's six member states to meet at Messina, Sicily, from June 1 to 3, 1955. There they agreed to explore a general common market and a joint organization for atomic energy, and they appointed Belgian Foreign Minister Paul-Henri Spaak to chair an intergovernmental committee that would turn the idea into a workable plan. The shift from a defence community to a customs union was itself telling: governments already accustomed by Marshall Plan aid to coordinating economic policy simply changed terrain rather than giving up on unity.

The Spaak Report and the Road to Val Duchesse

Spaak's committee worked for roughly nine months, and its report, approved by the six governments on April 21, 1956, became the blueprint for what followed. Rather than integrating industries one sector at a time, as the ECSC had done with coal and steel, the report recommended a horizontal approach: a general customs union with a common external tariff, built up gradually so that no single national economy would be shocked into collapse. The Venice conference of foreign ministers endorsed the report in late May 1956 and authorized full treaty negotiations, which opened at the Château de Val Duchesse outside Brussels.

Those negotiations were not a formality. French negotiators, wary of exposing a protected economy to German and Benelux competition, pressed for safeguard clauses, a transitional timetable, and the inclusion of France's overseas territories in an association arrangement preserving colonial-era trade links. France also tied its support for the common market to a parallel Euratom treaty, since planners hoped pooled research would deliver nuclear technology for both civilian power and an eventual independent arsenal. West Germany's Konrad Adenauer treated economic integration as the surest path to full political rehabilitation for a state only a decade removed from total defeat. Britain, invited to the Messina talks, chose not to join, preferring to keep control of its own trade policy and Commonwealth ties — a decision that shaped the Six's early years and foreshadowed the long dispute over British membership that would follow.

Six Signatures on the Capitoline Hill

By March 1957 the text was settled, and the six governments arranged a signing ceremony designed to carry symbolic weight: Rome, the city that had once ruled the same territories the new Community now spanned. On March 25, in the Palazzo dei Conservatori, Christian Pineau and Maurice Faure signed for France, Konrad Adenauer and Walter Hallstein for West Germany, Antonio Segni and Gaetano Martino for Italy, Paul-Henri Spaak and Jean-Charles Snoy et d'Oppuers for Belgium, Joseph Bech and Lambert Schaus for Luxembourg, and Joseph Luns and Johannes Linthorst Homan for the Netherlands. Two separate treaties were signed that day, one founding the EEC and the other Euratom, though both are conventionally remembered together as the Treaty of Rome. Ratification followed through the winter, and the treaties entered into force on January 1, 1958.

What the Treaties Actually Built

The EEC treaty committed its six members to a customs union and a common market built around the free movement of goods, services, capital, and labor — the "four freedoms" that remain the legal core of the European Union today. Article 8 set a transitional period of twelve years, divided into three four-year stages, during which internal tariffs would be phased out and a common external tariff phased in. In practice the customs union was completed faster than planned: internal tariffs and quotas were eliminated by July 1, 1968, eighteen months ahead of schedule. The treaty also set out objectives for a future common agricultural policy, though the detailed mechanism — price supports and market intervention — was not agreed until 1962.

The treaty established a Commission to propose and administer policy, a Council of Ministers to decide, a Common Assembly (forerunner of the European Parliament) to provide oversight, and a Court of Justice to settle disputes between members. Walter Hallstein, the West German jurist who had led his country's delegation at Val Duchesse, became the Commission's first president in January 1958 and spent nearly a decade pushing the young institution to act with more independence than some member governments were comfortable granting it. That tension between supranational initiative and national control resurfaced decades later, for instance when the Commission's first attempts at computerized governance ran into resistance from member states guarding their own administrative sovereignty. The Euratom treaty pooled research funding and nuclear materials among the Six, but never delivered the joint reactor program French sponsors wanted, as national programs — especially France's own weapons effort — diverged from its cooperative aims.

Chronology

Conclusion: A Narrow Bargain With a Long Reach

The Treaty of Rome was not written as a founding constitution, and its authors made no claim to have ended the nation-state in Europe. Some historians, following Alan Milward, read it instead as six governments using shared institutions to strengthen their own states and economies, not as a first step toward a federal Europe dissolving national sovereignty. Whichever reading one prefers, the treaty's practical effect was to lock France, West Germany, Italy, and the Benelux countries into a legal relationship that outlasted every government that signed it. The customs union it created was completed ahead of schedule; the Commission it established grew into a genuine executive; and the "four freedoms" it wrote into treaty law became the template against which every later step in integration, from Britain's 1973 accession to the passport-free travel later built by the Schengen system, would be measured. Six delegations on the Capitoline Hill could not have promised the European Union that followed, but they wrote the clauses that made it possible.

Frequently asked questions

Why is it called the "Treaty of Rome" if two treaties were signed? On March 25, 1957, the same six governments signed two separate instruments in the same ceremony: one establishing the European Economic Community and one establishing the European Atomic Energy Community, or Euratom. Because they were signed together in Rome, both are conventionally referred to as the Treaty of Rome, though lawyers and historians sometimes distinguish them as the "Rome Treaties" to be precise.

Why didn't Britain join the EEC from the start? British policymakers were invited to the Messina talks but declined to join the negotiations that followed, preferring to protect their trade policy independence and their trading relationships within the Commonwealth rather than commit to a customs union and common external tariff. That choice left European integration to the original Six and set up Britain's later, repeatedly frustrated attempts to join, which did not succeed until 1973.

Did the Treaty of Rome create the euro or the European Parliament? No. The 1957 treaty established a Common Assembly with advisory and oversight powers, which only gained direct elections in 1979 and the name European Parliament later still; a single currency was not seriously negotiated until the Maastricht Treaty of 1992, decades after Rome.

Why did France insist on the Euratom treaty alongside the common market? French negotiators made the customs union conditional on a parallel atomic energy treaty because French planners wanted pooled European resources to support both a civilian nuclear power program and, eventually, an independent French nuclear weapons capability. In practice Euratom's joint research ambitions faded quickly as national nuclear programs, particularly France's own, diverged from the treaty's cooperative framework.

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