Horseshoe Canyon Lean-to Aaron Schoenberg, George Sheedy & Dean Gletsos. Note the advertised yellow sign to Shaw's Lodging in Monson on the side of the lean-to. This shelter is located on the West Branch of the Piscataquis River. Also, the sign indicates the mileage to the blue spur trail to Monson in 7.7 miles north of here. Celt's mileage on his write up of his photo of 4 miles is incorrect. It is 4 miles south of the Blanchard-Shirley Road crossing. Monday, Sept 27, 2004.