Obviously the actual frontage of a Division will vary with the number of Brigades and Regimental strengths although Robert's 900 yards seems a tad tight to me. Anderson's Division at Gettysburg stretched over a mile and half but numbers alone don't tell the tale. Finding Division's in the Wilderness was quite a task never mind the Commander!
Which is what started me thinking on if there was some form of SOP where messengers went to a known location and then tried to find the individual if they were not present.
Of course matters varied, Divisional commanders got shot and even captured at the front but some also stayed at the rear and got quietly hammered, while it all happened elsewhere.
Size of an HQ or the Division is not really the question. Yes, today Divisional HQs are big and so are the Divisions but that's evolved along side modern Comms, which is kind of my point.
Corps HQs were supposed to be at a fixed point so messages had a destination. Didn't mean the Corps commander had to be there all the time, it just gave a staging post where Staff could take over responsibility for tracking the man down.
Did a Divisional equivalent exist in action, not in Camp.
I also find the matter of Staff size interesting. I'm guessing that was a variable too. Scott seems to suggest there was an Army standard. Where are the regulation allowance numbers to be found?
In the Napoleonic British army, Brigade commanders only had one or two Aides that were on the payroll but there were often others serving.
Taking one Civil War example at random, in Pfanz's book on the First Day at Gettysburg, there's a photo of Gamble's Staff – all eight of them. (Assuming Gamble is in the photo). Even if three of those shown were the Regimental commanders (the photo isn't captioned by individuals) that's still five officers for a Brigade.
So assuming a Division was as large if not larger, was there not a role for one or more to be at the HQ directing comms traffic?