Beside it, the impact even of Mr Clinton's triumphal visit to the province in November 1995 will pale. Yesterday's agreement is not an American deal, based on American proposals. But without America's backstage prodding, without the Clinton Administration's efforts as a "facilitator" it might never have happened at all.
Back in 1992, this kind of history-making was not even a gleam in the Clinton eye. His talk of naming a special US envoy to Ulster was a shameless pitch for the Irish-American vote; no-one doubted this gentleman's main task would be to further the nationalist cause with which Americans, as fellow victims of British colonialism, instinctively identified. After the election of course, no envoy was ever sent.
But the political calculation was impeccable. What downside was there in tackling Northern Ireland? In the end, the British would have to grimace and bear it. Success would be a prize beyond price. And if he failed - so what? Clinton would merely join the enormous club of statesmen who hadn't solved the Irish Question.
Then something happened. Bill Clinton started to take Ulster seriously. Maybe it was his Irish ancestry, maybe the fact that he witnessed the start of the Troubles in 1969 from close up, as a Rhodes Scholar at Oxford. But for whatever reason, backed by the Kennedys and the rest of the Irish- American lobby, the White House got involved.
At first, the slant was nationalist. A Kennedy went as ambassador to Dublin, and Clinton ignored the fury of the British and the advice of his own State Department to grant a visa to Gerry Adams. That step was instrumental in securing the first IRA ceasefire in August 1994. But the real transformation was when Washington grasped that there were two sides to the Ulster argument.
From 1995, David Trimble and the Unionists were given equal treatment. Gradually, the British came round to acknowledging that the Americans were something other than nationalist bulls crashing around the Irish china shop, and gradually, the US assumed the mantle of honest broker.
The annual St Patrick's Day festivities in Washington would become a cog in the peace process, an occasion where all parties could meet, where Irish eyes smiled and Mr Adams and Gary McMichael of the Ulster Democratic Party, whose father had been killed by the IRA, could be seen in the same room.
Even in darkest moments like the Docklands bombing, the White House pulled every string to keep the sides talking, mixing threats to withdraw its "recognition" of Adams with the carrot of economic aid and investment if a deal could be reached. Now that it has been, few will begrudge Mr Clinton his share of the credit.Reuse content