This website shows many historical and war monuments, markers, plaques, etc. 182,000 and counting. I added the War of 1812 marker info today as it wasn't there before.
The most important sights in New York have all been erased by development but this is Gravesend Bay, shores of the first and largest major conflict of 1776 known as The Battle of Long Island. Of course Lady Liberty should mark this important location but she is dwarfed by Jersey's ever growing skyline, far left. British forces held this port for 8 months.