O'Hara's greatest claim to fame is a poem about death, written during the Mexican-American War. "Bivouac of the Dead" has since been quoted in memorial markers and plaques in over a dozen cemeteries, including Arlington National Cemetery. Originally written to honor Kentuckians who died, it has since been read as a general lament for those who are killed in battle. From that poem:
The muffled drum's sad roll has beat
The soldier's last tattoo;
No more on life's parade shall meet
The brave and daring few.
On Fame's eternal camping-ground
Their silent tents are spread,
And Glory guards with solemn round
The bivouac of the dead.
No rumour of the foe's advance
Now swells upon the wind;
No troubled thought at midnight haunts
Of loved ones left behind;
No vision of the morrow's strife
The warrior's dream alarms;
No braying horn nor screaming fife
At dawn shall call to arms.
Their shivered swords are red with rust,
Their plumed heads are bowed;
Their haughty banner trailed in dust
Is now their martial shroud,
And plenteous funeral tears have washed
The red stains from each brow,
And their proud forms in battle gashed
Are free from anguish now.
Rest on, embalmed and sainted dead!
Dear as the blood you gave,
No impious footsteps here shall tread
The herbage of your grave;
Nor shall your glory be forgot
While Fame her record keeps,
Or Honor points the hallowed spot
Where Valor proudly sleeps.
Yon marble minstrel's voiceless stone
In deathless songs shall tell,
When many a vanished age hath flown,
The story how ye fell;
Nor wreck, nor change, or winter's blight
Not Time's remorseless doom,
Shall dim one ray of holy light
That gilds your glorious tomb.