Caltexian, I believe that this is one of those enduring mysteries about the battle that has never been fully resolved. Nearly everyone seems to think Custer and/or Reno would have passed that morass by and not watered there, or they feel for some reason it's not an issue. Try explaining why they stopped a short time later to water at recorded places and not one of their group or survivors mentions stopping here (hartung morass) to water. The logic and even the math just doesn't add up.
The recorded distances to the morass is also frustratingly not simple, I think because long held perceptions, cloud where everyone thinks it is or should be. And this is also true about tepee's, of which there was more than one.
Benteen recorded that this morass was (feel free to correct as i'm doing this on the wing) about 8 miles from a tepee, the question is which tepee was he referring to.
Ray Mekeeta and a few of his associates (can't remember their names right off hand) published a book about one of those tepee's. It's rather rare and expensive, but well worth the read. This tepee it was determined was somewhere in the range of 3 to 5 miles up Reno Creek from ford "A". Many today think that his 8 mile reference was prior to his arrival there. The question must be asked: was his 8 mile reference to it, 'before' or 'after' his arrival there? When reading the accounts in the RCOI, Edgerly, Benteen and Godfrey seem to leave a distinct impression that this morass was 'after' their arrival at a tepee. If the above tepee was the one they referenced, which it could have been (not saying it is). Then 8 miles in Benteen's estimate and 6-7 miles in Edgerly's estimate would have placed them near the river (Edgely's 6 - 7 miles, some 3- 4 miles or more upstream from Ford "A"); or 2 miles past that point into the valley of the LBH beyond (in Benteen's 8 mile estimate).
In the above example Edgerly's estimate seems to fit well with what was known about distance, and that 4 miles or so back at a 45 degree angle should have placed them on trail somewhere near The Flats and the 2nd tepee about 1 mile up Reno Creek from Ford "A".
Benteen seems to imply, as do the others, that they at first rode past this morass ( which could explain Benteen's lengthier estimate) and it was only after they had turned back did they see the pack train about 1 mile from this morass. Where they then watered at this morass for about the time it took the lead mules of the pack train to get there, whereupon they left.
The key to this is how they explain in letters to their wives about this morass and at the Inquiry about whether it came before a certain tepee - somewhere, or after. It is strongly suggested as I read it - 'after'.
One last thing to consider.
Benteen, Godfrey and Gibson all say that they arrived at the destination where Benteen had been sent. Benteen never claims to have observed the "valley", and tells different distances from where he had been sent, ranging anywhere from 2 to 5 miles, to that final destination, but clearly implies by his turning back statement that he did reach it before turning back. Godfrey and Gibson by their statements tell nearly the same story. That they arrived at the stated destination and turned back. Edgerly doesn't exactly state this, but it is virtually the same story as Benteen's with variations.
Mcdougall's estimate to the morass was about 3 to 4 miles, if I remember correctly. When one places this into context with what the others said, and indeed Benteen and troops only discovered this morass on their way back after having reached the destination that Custer had sent them to, then McDougall's estimate starts to make one wonder; is this 4 mile range perhaps more correct than others, as it gave them time to get there while Benteen and troops went beyond and then came back.
Last. The Indians Benteen, nor apparently no one else in his battalion saw while on their trek, would have had to have been observed at some point in that ride before their arrival at the tepee - 1 mile from Ford "A", because they had been sent as Benteen to paraphrase mentioned it; over hill and dale to the left of the trail. Those hills off in that direction would have, had to have at some point given someone in his battalion the chance to have observed either 1) the Indians fleeing down Reno Creek in advance of Custer's column or 2) the Village and all those stirred up Indians in advance of Reno's charge.
(Just my opinion, mind you. And not that it is necessarily correct
)