Sounds like a half-mapper (ie approx 17"x22") or else a full one-mapper that has a lot of charts and tables and less map area.
I presume you want full coast-to-coast, for doing the somewhat speculative New Mexico - California campaign, or do you just want West to somewhere in the midst of Texas and Kansas?
The only strategic level ACW hex-and-counter game of which I am aware is the old classic Victory Games' The Civil War
This is the right hex area, but is not coast-to-coast and does not show New York City or Chicago. But I would say for all real intents this still well covers the ACW strategic scope.