In order to best prepare for his planned Day 2 attack, Lee needed to know where the Union left flank ended. Early in the morning, he had dispatched one of his engineers, a CPT Johnston, to scout that flank.
History does not well record what Johnston did that morning, only what he told Lee upon his return. Later in life Johnston would claim that he had climbed partway up the huge pile of rocks known as Big Round Top. This is somewhat doubtful for a number of reasons. Although it was the undoubtedly the highest terrain point at the southern end of the series of hills, it was not a particularly good observation post. Its lower slopes were quite heavily wooded and even higher up it would have looked down on the even more heavily wooded southern end of Little Round Top. The bulk of Little Round Top would not have been visible from that vantage point. The Peach Orchard perched on the hill at Emmittsburg Road and the closer Rose Woods would have been in view but their density might have obscured any troops. It is far more likely that Johnston took the faster and easier route to the top of the southern end of Seminary Ridge. From there, he would have been looking down on the Orchard at his feet and would have had a clear view of all of Little Round Top except its heavily wooded southern tip. A wheat field would have been peeking out from the north of Rose Woods and the pasture land to the north would have been completely exposed. The irony is that Johnston saw virtually nothing. Little Round Top appeared to him to be completely unoccupied (Sickles men were out of sight on the inner slope). He returned to Lee’s HQ and reported that he saw only a small group of Union soldiers in the vicinity of the Rose Woods. (This was probably part of MG Humphrey’s division performing a recon of the area for Sickles.) This led Lee to believe that Meade had yet to extend his line beyond the southern end of Cemetery Ridge and that he (Lee) had an open avenue to displace that flank.
Had the Union line been on Emmittsburg Road as Lee assumed (and as shown above), his plan of attack would very likely have succeeded! Of course Sickles had something to say about that.
I’ll describe in a later ALT Hx section how I envision Day 2 might have gone had Sickles not been there when McLaws arrived. Given the actual disposition of forces, it likely would not have gone well.