The Portland Formation is an Early Jurassic sequence in Connecticut and Massachusetts composed mainly of sandstone laid down first in lakes and later on a river floodplain. More than 4 kilometres thick, it preserves about 4 million years of Earth history from the Hettangian into the Sinemurian and records sedimentation in the northeastern United States during the early age of dinosaurs. It is best known for fossil traces, especially numerous well-preserved dinosaur footprints found with the underlying East Berlin Formation, along with tracks of other animals and dinosaur coprolites. In 2016, Robert E. Weems and colleagues proposed reclassifying it as the Portland Group.