On July 1, 1863 the little town of Gettysburg, Pennsylvania got 164,000 unexpected visitors.
Crews there are getting ready for the onslaught of visitors to watch 3 days of reenactments of the battle of Gettysburg.
Historians agree it was a turning point in the Civil War, and some 15,000 reenactors will recreate the battles on the site.
There are even some 300 international reenactors from 16 different countries expected to attend.
Grandstands were brought in from the U.S. Open because so many people are expected to show up, and 275 porta-potties have been situated around the area.
Even local tee-shirt shops are churning out the souvenirs for the event that only happens once in 150 years.