Distinct features are a long bill with a slight downward curve, with adults being brown on the back and rusty-brown on the face and breast with a dark brown cap. They also have a white throat and a light belly with barred flanks. Immature birds are light brown on the head and darker brown on the back and wings.
They breed in marshes in eastern North America. The nest is a raised platform built with marsh vegetation and covered by a canopy. The king rail interbreeds with the clapper rail where their ranges overlap; some researchers believe that these two birds belong to the same species.