Six major hypotheses have been advanced to account for ground slate industries containing knives, lance heads, and projectile points, found on opposite sides of the North American continent. Certain of these hypotheses assume genetic connections; others postulate separate sources and developments for such artifacts in the Northeast and North Pacific areas. A recent study of the cultures involved, chiefly Borden’s (1962) Vancouver data, has indicated that: (1) ground slate artifacts made their initial appearance in both areas at about the same time; (2) the respective typologies are quite dissimilar; and (3) possible bone and/or chipped stone prototypes for certain of the specific ground slate forms exist in each area. These data suggest independent origins and developmental histories.