 The west slopes of Lyon drain into Standish Brook, thence into Middle Kiln Brook, Upper and Lower Chateaugay Lakes, the source of the Chateaugay River, which drains into the Saint Lawrence River in Canada.The northwest slopes of Lyon drain into Separator Brook, thence into Upper Chateaugay Lake.Lyon Mountain Mountain Fire Observation Station, built in 1917, still stands atop the mountain, and can be accessed by hikers.