Portland Head light, Stereoscope Card.19th century. Boston Public Library Collection.

The collection/dataset uses media from the world's largest public domain source Picryl.com. It is made in two steps - first manually picked, and then, found semi-automatically, with aid of image recognition, it comprises of more than 5,000 images. Everything in the collection is in the public domain, so there is no limitation on the dataset usage - educational, scientific, or commercial.