I guess I have a personal interest. My Great Grandfather Alphonzo Burton Hutto was severly wounded with Company "K" 13th South Carolina Inf. in that charge of July 1st. He was captured by Federal forces in the hospital (Lutheran Seminary) on July 5th.
I had specifically made a trip to Gettysburg to at least look over the site of this engagement, and was disappointed that it was so poorly interpretated. In fact if I had not purchased a book "Gettysburg, A Testing of Courage" by Noah Trudean, the day before, which had an excellant map of the situation at 4:05 pm, July 1st on page 238, I would not have been able to identify the site based upon the National Parks interpretative signage.
Once I was able to identify the site it was readily appearent that the Union position was a strong one and that McGowan's/Perrin's brigade would have had to advance across an open area down into a gully and then up into the face of the Union defences. That would have been no small feat to have accomplished. And as I understand the reports the Union artillery was quite effective on this portion of their line.
As for why this isn't intrepreted better? The National Park at least owns the land were the Union were positioned and there is some general signage at that point already there as it is. But nothing about the Perrin bgd-Biddle bgd engagement. And signage surely doesn't cost that much maybe $2,000 or $3,000 a sign unless the cost in Pennsylvania are a lot more inflated than they are were I live for such historical interpretative signs. We are not talking about a huge monument here just an informational sign.