The Longton (Kans.) Gleaner (Dec. 30, 1881), p. 2, prints the earliest documented text, five years after Francis Maynard is said to have written the song. (See the "Live in the Nation?" thread: Maynard's own 1911 text is not identical.)

It would be interesting to know who requested publication in 1881 and why. According to the U.S. Census Bureau (via Wikipedia), the population of Longton in 1880 was 255.

                                 THE DYING COW-BOY
                                              --
                                 (Published by request)

        As I rode down by Tom Sherman’s bar-room,
        Tom Sherman’s bar-room so early one day,
        It was there I spied a once handsome cow-boy,
        He was draped in white linen as though for the grave.

        Chorus.
        Beat the drum lowly, and play the fife slowly,
        Oh! play the dead march as you bear me along.
        Bear me to the graveyard and lay the sword o’er me,
        I am a young ranger, I know I’ve done wrong.

        I see by your outfit that you are a cow-boy;
       These words he said as I went riding by,
        Come sit down by me and hear my sad story;
        I’m shot through the breast and I know I must die.
        
       Go bear this message to my gray-headed mother.
        And drop the news gently to my sister dear.
        But not one word of this place do you mention,
        When they gather around you my story to hear.

        But there is another as dear as my sister,
        Will bitterly weep when she hears I’m gone                  
        But there is another may win her affection,
        I am a young ranger, I know I’ve done wrong.

        Once in my saddle I used to go dashing.
        Once in my saddle I used to look gay;
        I first took to drinking then took to gambling,
        Got into a fight, and now to my grave.

        Go gather around you a crowd of gay cow-boys,
        And tell them the tale of their comrade’s sad fate.
        Tell each and all to take timely warning
        And quit their wild ways before it is too late.

        Go bring to me a cup of cold water,
        To bathe my flushed temples, the poor fellow said.
        But ere I had reached him the spirit had left,
        It had gone to the giver, the cow-boy was dead.

                                 LAST CHORUS.

         We’ll beat the drum lowly, we’ll play the fife slowly,
        We’ll play the dead march as we bear him along,
          We all love our comrade, so brave and so handsome,
        We all love the cow-boy, although he did wrong.