Particularly for the Confederates, these positions are somewhat tentative. However:
24th October (i.e. before the campaign itself starts)
I've co-located DH Hill and Walker because I have no better information. It is possible neither of them were here yet.
At this point both armies are in a defensive posture for the most part, along the upper Potomac. McClellan is spread out firstly because his intent up to this point was to strike into the Shenandoah (he switched plans in the last couple of days and got them approved late on the 23rd) and secondly because this way he can counter a move by Lee to cross the Potomac west of the Blue Ridge.
Lee is mostly covering the lower Shenandoah Valley, and is spread out partly to allow for forage. (Though Lee himself is actually down in Richmond.)
25th October:
9th Corps moves to Berlin, where the pontoon bridge is being set up. Not all the corps moves in one go, and the bridge is still being built.
I now have Walker localized so have put his force at Paris.
26th October:
1st Corps also breaks camp, concentrating on Berlin. 9th Corps pushes over the now-bridged river to control the debouche.
My guess based on the later movements is that the engineers may now have gone to Harpers Ferry to build the bridge over the Shenandoah, but this is not confirmed.
27th October:
9th Corps finishes crossing. 1st Corps has supply deficiencies to rectify, and does so while on the rail line; there is also some of the crossing of wagon trains here.
28th October:
Longstreet starts moving. (Some of the positions for Longstreet's movement are approximate.)
The news of Longstreet breaking camp causes McClellan to freeze his movement in case Longstreet is striking north (in which case he will need everything he has available north of the Potomac) and he sends a brigade-strength cavalry recce to investigate.
29th October:
With confirmation that Longstreet is not moving north, this is when the forces along the upper Potomac start peeling away. 9th Corps moves out to cover the whole of the upper Loudoun Valley (and possibly also to cover the terminus of the bridge at the mouth of the Shenandoah river).
This is the last point at which Pickett's position is estimated; after this point I'm pretty sure.
30th October:
1st and 2nd Corps cross much of their fighting echelon. Meanwhile Longstreet is moving south rapidly.
31st October:
At this point the only defensive forces along the upper Potomac are Morell's small force. 12th Corps is at Harpers Ferry and will be left there.
2nd Corps finishes crossing.
Walker begins moving south. All of what will formally be Longstreet's Corps next month are now on the move to Culpeper; Hood has split in half with the half going into quarantine assumed to be taking the Valley Pike route down to Swift Run Gap.
1st November:
5th Corps crosses much of their fighting echelon, and 6th Corps reaches the pontoon bridge. There are now four Union corps over the river and moving south.
The "traffic jam" at Jefferson is an approximation of position, and Pickett could have preceded Walker or they could have taken parallel routes. The position is only roughly correct.
2nd November:
2nd and 5th Corps acting as a single wing under Porter seize Snickers' Gap (AP Hill is on the other side of it). 9th and 1st move past while the gap is masked.
6th Corps follows 9th and 1st.
There are now Confederate troops at Culpeper itself. Notably, DH Hill is still in a position to block the approach to Culpeper, which would let him at least delay a single-corps dash south.
At this point DH Hill is worried that Union troops may enter the Valley and cut off his retreat.
3rd November:
5th Corps demonstrates against AP Hill, then returns to the gap. 9th and 2nd collect ready to go after Ashby's Gap, and push DH Hill away from his position at Upperville; the operations here are as much capturing the gap as if there'd been a major battle.
One division of 1st Corps is pushed forwards to take a crossing of Goose Creek.
4th November:
2nd Corps takes Ashby's Gap, and DH Hill pulls back into the Shenandoah before marching for Front Royal. 5th Corps is still holding Snickers' Gap.
Walker moves south away from Culpeper itself, which may indicate that Lee's plan is to keep moving south.
5th November:
9th Corps marches to take control of Manassas Gap. There are now Union corps controlling all the main gaps in the Blue Ridge Mountains, and meanwhile 1st Corps is preparing to take Warrenton.
Lee returns from Richmond (to Culpeper).
6th November:
With the bulk of the army past and 1st Corps taking Warrenton, the Blue Ridge mountain gaps are now no longer necessary. 2nd, 5th and 9th Corps all pull away from the mountain gaps, and some of 9th Corps reaches the north fork of the Rappahanock to sieze control of a bridge there.
Lee's letter to Jackson around this time tells him to march south, but is ambiguous; when Lee writes to the Confederate SecWar the next day however he is clearer that he meant for Jackson to move.
7th November:
The Union army is concentrating on Warrenton, and 9th Corps does the same thing it did earlier in the movement - secure the area on the far side of a bridge.
At this point McClellan is relieved in command, but his already-issued march orders are followed for the duration of the 8th and 9th.
(This is also around when the other half of Hood reaches Gordonsville.)
Lee's interpretation of McClellan's movements, to Stuart, is that it doesn't seem likely that McClellan will be trying to interpose between Jackson and Longstreet. He also says that if McClellan does push Lee back he'd have Longstreet fall back through Madison to make a junction with Jackson coming out of Swift Run Gap.
Jackson may at this point have ordered a concentration on Winchester to strike north (we mostly know that he cancelled the concentration overnight 9th-10th November)
8th November
6th Corps holds the Thoroughfare Gap area to shield Gainesville while 5th Corps goes through.
Lee is more explicit that Jackson must move now (he won't).
Walker has shifted to Madison Court House, possibly to defend the route by which Lee thinks he may have to retire.
9th November:
Much of the Army of the Potomac is now concentrated at Warrenton. 6th Corps leaves Thoroughfare Gap to 11th Corps (currently around Gainesville) and is under orders to move to Warrenton as well, but the change of command stops the army moving.
3rd Corps is also around Warrenton at this point - components of the corps have been seconded to 9th Corps or arriving by rail, but by now the whole corps is present (albeit spread out).
Interestingly, on this date (9th November), Lee told Stuart that there were dispatches to the effect that McClellan was concentrated "in the vicinity of Piedmont" (a theme he repeated to the Confederate SecWar on 10th November). This is a bit off...
Later on the 10th Stuart discovered a division-plus of 9th Corps at Amissville.