The Iron Brigade charges up McPherson's Ridge during the 150th Anniversary of the Battle of Gettysburg on July 1, 2013.

The National Park Service is celebrating its 100th anniversary this year, and the folks at Gettysburg National Military Park want to remind you not to take any stones from the park.

Well, for one reason, they re cursed.

That s according to a blog post by Maria Brady, a park ranger at Gettysburg.

Brady writes that the park sometimes gets packages in the mail with people returning rocks they took— which is a violation of federal regulations and can result in $130 worth of fines and fees, she points out— and those packages usually have letters.

In one letter, sent to Gettysburg in May, a man admits that he and his wife took three stones.

The text above is a summary, you can read full article here.