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

to the river through the erie canal into lake erie to the erie canal to the hudson to the ocean that is an incredible highland, and the hub is toledo. so steven mason was the first governor in the territory of michigan to challenge that adjustment that ohio made, and the governor of ohio, robert flucas, said we are a state, you are a territory, you cannot alter a state line without our consent. i'm abbreviating things enormously. maysan in effect said and whose army is going to stop us? and he called the territory militia which my army is going to stop yours and he called up ohio's militia and we had the to face-to-face on what is known as the toledo war, which almost sparked the full scale combat but didn't because congress quickly intervened and said to michigan how about this? we will give you this peninsula coming off -- wisconsin. hardly anyone even living there. >> how about you let ohio have its way and to simplify michigan finally said okay we will take the deal. robert lucas went on to become the territorial governor of iowa, and it was in that capacity that we begin to return to quite a route yet to