The nearby village of Tuxedo Park (just beyond view of the hills from where you are standing) was conceived by Pierre Lorillard IV as a planned community in the 1880s with the intention of creating a hunting and fishing resort for New York City's newly rich residents. The resort attracted a number of the financial, industrial, and social leaders of the day. Many of the "cottages" were designed by well known architects of the time, and residents included the Posts, Morgans, Astors, Dukes, and other well off families of the era. One year at the annual Autumn Ball, Griswold Lorillard wore a tail-less dinner jacket that had become popular in England. Supposively one fellow at the Ball asked of another "Why does that man's jacket have no coattails on it?", recieving the answer "He is from Tuxedo". The first gentleman misinterpreted and told all of his friends that he saw a man wearing a jacket without coattails called a tuxedo, not from Tuxedo. The name would stick, and the popular dinner suit would become known as the tuxedo.
You are looking for a small cache close to the river bank. Parking is nearby, if you can figure out how to get there. As stated earlier, you cannot approach from the nearby NYS Thruway. Beware of potential fishing muggles.