According to the press release, "Dedicatory services will be held on Saturday, September 19, at 11:00 a.m. eastern daylight time (EDT) at the site. President Russell M. Nelson, President of the Quorum of the Twelve Apostles, will give the dedicatory prayer."
This is a tremendously important site. Among many other important events, it was here that Joseph and Oliver translated the Book of Mormon.
Here is more from the press release:
"Joseph and Emma Smith moved to Harmony in December 1827 to escape persecution for their religious beliefs. They lived with Emma’s parents, Isaac and Elizabeth Hale, until they purchased a nearby home with 13½ acres from Emma’s brother Jesse.
"In early April 1829, schoolteacher Oliver Cowdery came to meet Joseph and soon became his scribe. During the translation of the Book of Mormon, Joseph and Oliver went into the woods and prayed for guidance on the subject of baptism. In reply, the resurrected John the Baptist visited them on May 15, 1829, and ordained them to the Aaronic Priesthood. He then commanded Joseph and Oliver to baptize each other in the nearby Susquehanna River. A little later in a nearby area, the two men received the authority of the Melchizedek Priesthood from Peter, James, and John, three of Jesus Christ’s original Apostles.
"Also in Harmony, Joseph received 15 divine revelations that were later included in the Doctrine and Covenants. Joseph and Emma Smith moved from Harmony in August 1830. The home they lived in burned down in 1919 and is now reconstructed as part of the site."
Here's an aerial map of the site. Here are the coordinates if you want to see it on Google Earth: