Douglas A. James, University Professor in biological sciences, explains:

        Crows and ravens are in the same avian family, Corvidae, along with jays, magpies and others.  The Corvidae are classified as songbirds, the common raven being the largest songbird.

Crows usually are all black, but worldwide some species have gray or white patches.  All raven species are totally black and have a jagged ruff of feathers on the chin below the beak.  Most raven species have a wedge-shaped tail in flight.  Crows lack the throat hackles and have rounded tails. 

Voices are very different.  Ravens emit a loud harsh guttural croaking sound. Crows are less grating: the American crow in Fayetteville says "caw caw" and the fish crow at Lake Fayetteville repeats a high pitched short nasal sound.  Raven species are generally larger than crows, but not always.  The Chihuahuan raven of our southwest is equal in size to the common American Crow.

Common ravens, immortalized by Edgar Allen Poe and vice versa, occur in the northern parts of the northern states, across the Canadian forests, through Alaska, down the eastern and western mountains, and through Siberia and Europe, but not in Arkansas.  They previously were found in England around the Tower of London, but no longer.  The ones tourists see there now are imported.

Crows are featured in the Alfred Hitchcock movie The Birds.  However, the movie was filmed at a coastal location north of San Francisco where only ravens occur, not crows.