Book excerpt: Clapper rails (Rallus longirostris) are widely distributed in coastal marshes and river valleys of North and South America and the Caribbean. Seven of the 26 subspecies currently recognized by various authorities occur in the western portions of the United States and Mexico. Three races are classified by both the Department of Fish and Game as "endangered". These subspecies are the California clapper rail, the Light-footd clapper rail, and the Yuma clapper rail. Our investigations of these endangered forms included a review of pertinent literature and an examination of specimen data in selected museum collections. This paper deals with primarily with the endangered forms but also attempts to describe the general relationships of all western clapper rails.