Where was the first Civil War monument erected?

I recently visited the Manassas Battlefield Park. The First Battle of Manassas was fought on July 21, 1861---so it was one of the earlies large battles of the war. Since it was close to Washington, there were many markers and monuments built on it. One of the large monuments on top of Henry Hill was built in June 1865. But there were other monuments or markers that were placed in sites where General Bee was killed and for other events in the battle. I don't know when they were placed.

There was a monument built at Murfreesboror, Tennesse, during the war by occupying Union troops. But I don't have the date for that. So I'm not sure when the FIRST one was built.