My great-great grandfather Norman Nelson Blake was with the 136th Ohio Infantry defending Washington D.C. against your great-great uncle and Jubal Early. He was stationed with the Northern Defenses of Washington - Ft. Ellsworth, near Ft. Stevens.
He was 32 yo. He enlisted after serving as a "Squirrel Hunter" defending against Morgan's raid through Ohio.

Small world. And, as mentioned, neat to have the location and photo.