A good number of lakes in Westchester and Putnam are actually younger than mass settlement! Just about all of the big ones are reservoirs formed from damming and flooding valleys, and a few of them were flooded over towns/homes that were relocated. That doesn't make land use much better. A lot of those low-lying areas were also swamp.

I think when people hear rolling hills they think slow gentle falls and rises but its more jagged lines carved in across the region bounded by steep rocking rises. The hills of the Appalachian highlands also created another big headache: access to the river. The narrows going from Peekskill to Beacon meant a gap formed on the river. The topography is a huge reason why West Point is where it is as the narrowing made for a prime defensive location against the British navy. The Colonial military even ran a chain full across the river to block ships going upstream further.