John James Audubon observed: “Wherever our Crow is abundant, the Raven is rarely found, and vice versa. From Kentucky to New Orleans, Ravens are extremely rare, whereas in that course you find one or more Crows at every half mile. On the contrary, far up the Missouri, as well as on the coast of Labrador, few Crows are to be seen, while Ravens are common. I found the former birds equally scarce in Newfoundland.” For as long urban sprawl and development limits nesting opportunities in such isolated places as the ledges of cliffs and the sides of deep ravines and high up in tall conifers and crows are keeping guard, Ravens will likely keep away from the eastern United States.
Plate 101 – Raven
Plate 101 of the first edition of "Birds of America" by John James Audubon.