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]

Moby Thesaurus II by Grady Ward, 1.0:

33 Moby Thesaurus words for "towpath":
   alameda, beaten path, beaten track, berm, bicycle path, boardwalk,
   bridle path, catwalk, esplanade, fastwalk, foot pavement, footpath,
   footway, garden path, groove, hiking trail, mall, parade, path,
   pathway, prado, promenade, public walk, run, runway, rut, sidewalk,
   towing path, track, trail, trottoir, walk, walkway