Sandy Hook is government proving grounds? So says a documentary from 1897!

"This is one of the most remarkable views that has ever been taken, and shows a modern high-power gun in act of discharge. The immense gun, weighing 67,000 pounds, is seen to rise in the air, discharge its projectile, and sink back behind the fortification ready for reloading. Showing the loading, raising, firing and recoil of the big ten-inch coast defense gun at the Government proving grounds, Sandy Hook. A remarkably fine picture."

A documentary from 1897?
[link to www.imdb.com]