I was looking in the 1886 Railroad Gazette and I found a two page article on the South Park High Line.
Included are two maps, a drawing and a profine of the line.
The article is on Page 886 and 887 and the magazine can be found at:
http://babel.hathitrust.org/cgi/pt?id=mdp.39015013053692#view=1up;seq=16There is also a short article on traffic on page 150.
Ken Martin