they first went to the hudson highlands, but 150 years later, it went to the delaware highlands. and really diverted the water that normally went to philadelphia to new york city. i don't think they anticipated that. narrator: the majority of new york city's drinking water comes from watersheds in upstate new york. a watershed is the area of land where water from rain or snow melt drains downhill into a body of water. mountains act as a funnel to feed rivers and lakes. and in this case, reservoirs. in the new york city system, water is collected and stored in 19 reservoirs, which can hold more than a year's supply -- over 580 billion gallons of water. almost all of the system is fed by gravity, without the use of energy-consuming pumps. valves open to regulate the flow into the 85-mile-long delaware aqueduct -- the longest tunnel in the world. at hillview reservoir... the water is partitioned into another giant tunnel system. where it travels deep below manhattan. the pressure built up by gravity from the mountains pushes the water upwards toward the surface through vertical shaf

been further to the right of the river it's the hudson highlands.from 1776 until 1782, most of the revolution in middle of the atlantic states was stalemate. the british occupying manhattan, and george washington's army stretched from peekskill, new york, all the way down to millbrook, new jersey. and neither side for various reasons want to have it out with the other side. the supplies for all those military people in those hills in new jersey crossed the hudson river north of west point. and west point which is up on a high bluff where the river makes a very sharp, two very sharp turns, patty cheyne built across it, all for the purpose of keeping a very powerful british navy from going up river beyond west point where he could interdict the supply line. so there's a reason why the u.s. military academy is a sanctum santorum, the regular u.s. army is west point. it was the strategic key to victory in the american revolution and. and what you had was arnold and peggy and i think to secure -- conniving to secure the facili facility. >> peggy was doin