I've noticed in that a lot of American Civil War AHs, if the Confederates do attack Washington, they always do it at Fort Stevens? Grant Comes East and Guns of the South are the two that spring to mind.
Now, is there anything about Fort Stevens or its location that makes it a better target for the South, or is it just that there was a battle at Fort Stevens OTL, so authors just do the lazy thing and use the same fort?