The studying is ongoing and I can comfortably say I know the order of battle for the 1st Corps to the regimental level, and now I start studying the 2nd Corps.

One of the things I enjoy doing at Gettysburg (in particular) is finding period graffiti on the battlefield.  Some (like Coble Rock by Spangler's Spring) are well known, others, not so much.  Devil's Den was so covered with graffiti that when the Park Service finally obtained the property, they had to chisel much of the rocks there to remove it (look for period photos and you'll see what I mean).

For your viewing pleasure, here is some period graffiti that I've found (using reference material) on the battlefield.  For the record all pictures shown in this post were taken by yours truly.

This one is on the south wall of the McPherson Barn, if you can't make it out it reads:
JCT 143 PV
SMG Sept 12 1889
This one was found in 2004 by the son of a battlefield guide.  THe carvings are traced to Jonas C Tubbs and Singleton M. Goss.  Tubbs was a private when taken prisoner on the first day of the battle, Goss was a drummer boy who served throughout the war.

Again this is one not too many people see, mainly because this is from one of the less famous areas of the battlefield (not to mention the steep uphill walk to get here).  These are atop of Big Round Top.  They may not all be visible in this picture, but the names are:  J. Noble; J. Hinchcliff; J.Crumlish; and the initials WHG and WHH.
The identities aren't all known, but Hinchcliff and Crumlish are names of personnel who served in the Union Army, but weren't with units that fought at Gettysburg, maybe they were there for a reunion after the war?

This is up on Little Round Top, kind of in a hidden place but in plain sight (if you know where to look).  This is behind the 91st Pennsylvania Monument.  It commemorates the spot where Brigadier General Stephen Weed and Lt. Charles Hazlett died.  It's very faint, but reads as follows, "C. E. Hazlett Fell / Com'g Batt'y D U.S. Art'y in Battle / July 2nd 1863"

These next two I found on the Henry Spangler Barn while exploring last year.  I've never seen them written up anywhere, but that probably means I'm not looking in the right places.  They are period, but I have no clue who they are related to.  They read as follows:  "C.A.S. (reversed S) 1871" and what to me looks like "C. SP. 1875"

That's it for today, I'll post more pix later this week.