What is the significance of the names in Billy Collins’ poem “The Names”?

In “The Names,” our speaker is reflecting on all the people who were victims of the September 11 attacks on the World Trade Center in New York.  Collins speaks to the everlasting impact of this event by suggesting that these names are inscribed into every facet of life and nature – all that endures:  “Names printed on the ceiling of the night…Twenty-six willows on the banks of a stream.”  And indeed he gives a name for every letter of the alphabet, A through Z, with “X stand[ing], if it can, for the ones unfound.”  This is a further symbol of the ubiquity of the effects and the thoroughness of the tragedy; they stretch from the very beginning to the very end, they touch every element across the entire spectrum of humanity.  Nothing and no one was left untouched, unaffected, by the unwitting sacrifice of the victims.

And as “A boy on a lake lifts his oars./A woman by a window puts a match to a candle” – as life goes on – these names will be remembered in memoriam,

One name spanning a bridge, another undergoing a tunnel.
A blue name needled into the skin.
Names of sisters, brothers, mothers, and fathers,
The bright-eyed daughter, the quick son.
Alphabet of names in a green field.

Thanks to these names, to their lives, to their lives lost, those living on will be reminded – will learn from the tragedy, will feel sorrow and strive for peace – the peace of “a green field.”  The names are symbols, unforgettable, sobering, and inspiring.