The Collaborative International Dictionary of English v.0.48:

Towpath \Tow"path`\, n.
   A path traveled by men or animals in towing boats; -- called
   also towing path.
   [1913 Webster]

WordNet (r) 3.0 (2006):

towpath
    n 1: a path along a canal or river used by animals towing boats
         [syn: towpath, towing path]