A wizarding school located in the state of Massachusetts in the United States (Pm)
Located atop Mount Greylock, the tallest point in the state of Massachusetts, the school is attended by young witches and wizards from all over North America. It originated in the 1600s as a stone house with two teachers, the founders, and two students, their adopted sons. It has grown into being one of the premier centers of magical education in the world (Pm).
The image shown on Pottermore for Ilvermorny shows a turreted building, several stories high. It is unknown whether this image is accurate or not.
From the Web
Mount Greylock on Wikipedia