There are residences closeby, too.
Another thing that bothers me about this case, and it fits in with what a lot of have theorized about the timeline (and it's a short one), is the perp knew they would be found in a matter of hours. They were found roughly 22 hours after the SnapChat was uploaded. Not days, weeks, months, or longer. Hours.
Something I'm wondering about the SC pic of Abby:
Like others have stated, it does look artistic, maybe posed. It's a really nice photo. MOO, they were taking their time getting across the bridge, especially that SE end, the pic is taken, and let's say Libby does a quick effect or edit to it, before uploading it. Or maybe there were multiple pics, and she scrolled through them, found that one, touched it up a tad, then uploaded it.
They could have been off the bridge, already, when the pic was uploaded, in fact the perp may have been making his way across at 2:07 PM. Libby is already in her phone, anyway, scrolling through pics, uploading one or two, when the perp gets on the bridge.
They were dropped off around 1PM. SC pic is uploaded at 2:07. Judging by the distances involved, from the end of the trail to the SE end of the bridge, the girls could have made that distance, even walking slowly, in well under a half hour. So either the pic was uploaded instantly (unlikely), or Libby uploaded it at 2:07 PM.
MOO is the guy was on or close to the other end of the bridge at around the same time as the pic upload to SC.
Edit:
Judging by his steps in the images, it probably took the guy under 4 minutes to cross the bridge.