This has been a fascinating thread to an old Civil War buff like me, even though the original question seems to have disappeared long ago. Getting back to that: I'll have to get out my video tape of the Gettysberg movie and see if I recognize the fiddle tune. If it, indeed, is "Kathleen Mavourneen", I'm wondering about it's "authenticity" during the Civil War. Does anyone know where that song comes from and when it was written? I've always had the impression that it was one of those many "Irish" songs that were actually written by non-Irish persons for the American music hall public -- but if I'm wrong, please let me know. I have an old copy of "The Golden Book of Favorite Songs" that has the song with words attributed to Mrs. Julia Crawford, and music to Frederick N. Crouch. Neither name is familiar to me, but reinforces my feeling that it is a fairly modern "composed" song and not a true Irish folk song. I can find no date and wonder if it dates back to Civil War days.
As to the inquiry about Picacho Peak, as an Arizonan (for the past ten years) I am familiar with it. Briefly, in 1862 the Confederates tried to take control of New Mexico and Arizona and had thoughts of invading California. A Confederate force under Gen. H. H. Sibley marched up the Rio Grande from El Paso, won a victory of sorts at Valverde near Ft. Craig, moved on north and were finally stopped by a Union force moving down the Santa Fe Trail from Colorado at the battle of Glorieta Pass, not far from Santa Fe. Alvin Josephy in his book "The Civil War in the American West" refers to this battle as "the Gettysburg of the West" (which may be stretching things a little, but it was an important an interesting battle). Sibley's force then retreated back to El Paso.
Meanwhile a Union force under Colonel James Carleton marched east from California. Carleton, from Ft. Yuma, on the Colorado River, sent out a force of 272 men under Captain William Calloway to take Tucson. Some of Calloway's men commanded by Lieutenant James Barrett had a "brisk encounter with a small body of Hunter's Confederates among the saguaros and mesquite trees at Pichacho Peak, a fingerlike rock spire north of Tucson." Barrett was killed and Calloway withdrew until joined by Carleton's main force, which then advanced on Tucson. Hunter, outnumbered, withdrew his troops back to El Paso, and Carleton's army went on to occupy an abandoned (by the Confederates) Tucson. This ended the Confederate thoughts of invading California, and left the Union in control of New Mexico and Arizona for the remainder of the war. A "turning point" in the tide of war in the far west -- hence the "Gettysburg of the West" appelation, I guess.
R#2