I've always wondered this. Historical reenactments of Civil War battles and similar reenactments seem to have huge popularity (considering what they are). How, when, and why did these begin and become such a mainstay?
The first large reenactment happened in 1913 at Gettysburg; actual soldiers who fought during the Civil War, more than 50,000, filled the ranks. As long as a soldier was honorably discharged from either the Union of Confederate Army, being a combatant at Gettysburg wasn’t required, the soldier was welcome to particpate. Outside spectators were allowed as well.
One of the highlights of this event was the reenactment of Pickett’s charge. Around 500 veterans who participated during the actual charge, aggressors and defenders alike, lined the barricade and shook hands after the charge was complete. This was mentioned in Ken Burns documentary on the Civil War. As you can imagine, it was an emotional time for men on both sides and some of them broke down and cried during the finale.
Modern Civil War reenactments began to gain popularity in the 1960's, around the 100 year anniversary of the Civil War, and continued in the following decades. There was a general increase in interest during this time period in the Civil War as noted by the amount of books that were written.
The predominant reason for the reenactments is to continue teaching the history and tradition behind the soldiers, battles and reasons for the conflict. Many re-enactors also participate to get a sense of what life was like for the soldiers who fought. There are classes on how to talk, cook, shoot, and dress like a veteran.
A part I found interesting was the different levels of reenactments and how far people get into character. There are some re-enactors who are more casual in preparing for a battle and others who will stay in character the entire time. For example, these actors won’t consume any modern food while in character; they will only eat the food of that time period. In addition, these actors will talk, walk, and dress in exact accordance with a soldier of the Civil War. It’s quite a sight to see if you haven’t been to one!
In the interest of space I will stop writing here but would love to answer any follow up questions.
L.E. Beitler. Fiftieth Anniversary of the Battle of Gettysburg
R. Hadden. Reliving the Civil War
Edit: Added sources.
here's some info on naval battle reenactments in Rome
Were naval battles staged in the Coliseum?
and, just FYI in case you're interested in how widely-spread reenactments are: