The first recording was made by G. B. Grayson and Henry Whitter, 1927 Victor master 40303, released 1928 Victor 21139. Most 'folk' collections are based on this recording.
The lyrics posted by Gene in 2006 are mostly correct; the following copied from Norm Cohen, Long Steel Rail, contains a few corrections. Cohen was uncertain about line one of the last verse.

Lyr. Add: HE'S COMING TO US DEAD
Sung by G. B. Grayson and Henry Whitter, 1927

One morning when the office had opened, a man quite old in years
Stood by the express office, showing signs of grief and tears.

When the clerk approached him, in trembling words did say,
"I'm waiting for my boy, sir, he's coming home today."

[Spoken:] Take warning from this song.

"Well, you have made a slight mistake, and you must surely know,
That this is a telegraph office, sir, and not a town depot.

"If your boy is coming home," the clerk in smiles did say,
"You'll find him with the passengers, at the station just o'er the way."

Take warning, folks.

"You do not understand me, sir," the old man shook his head,
"He's not a-coming as a passenger, but by express instead."

Take warning, good people.

"He's coming home to mother," the old man gently said.
"He's coming home in a casket, sir, he's coming to us dead."

Then a whistle pierced their ears; "The express train," someone cried;
The old man rose in a breathless haste and quickly rushed outside.

Then a long white casket was lowered to the ground,
Showing signs of grief and tears to those who'd gathered 'round.

"Do not use him roughly, boys, it contains our darling Jack,
He went away as you boys are, this way he's coming back.

"He broke his poor old mother's heart, her sins have [?her fears have since] all come true.
She said this the way he'd come back, when he joined the Boys in Blue."

A lot of them come back that way, too.

Pp. 300-303, with brief musical score.

Cohen comments: " There is nothing in the text of this song to link it unequivocally with either the Civil War or the Spanish-American War."
Norn Cohen, 1981, Long Steel Rail, University of Illinois Press.