Yeah, good point... I remember an old abandoned concrete and stone fort at Popham Beach, Maine, built around the turn of the century. I used to go up to the beach there and hang out, on summer weekends, when I was stationed at the NAS in Brunswick, Maine. It's been quite a few years, but I recall reading some information plaque at the fort that spoke of it being built for defense purposes against coastal attack. This article puts it all in historical perspective. If you want to see turn of the century coastal batterry fortification again, get on the Bainbridge ferry and drive to either Fort Flagler or Fort Wagner State Parks. "Officer and a Gentleman" was filmed at Fort Warden State Park. The concrete fortifications they ran around on were turn of the century shore batteries.
Yes, good point... I overlooked the fact that we had similar coastal batteries built right here in my own state of Washington, though I wasn't sure of the date that these were built.
I had originally thought that these were built somewhat later, around the First World War, but I see now they were built earlier than that (and now I see the historical perspective, too).