We can find that 47 of the 63 largest manufacturing firms in 1909 were formed by consolidation from 1882 to 1904. Consolidation played a decisive role in the process of the emergence of modern large corporations. In this article I divide these cases of consolidation into four types according to three criteria : (1) pattern of strategic evolution ; (2) percentage effect of the standard firm on the market or economy of scale and speed ; and (3) incentive to diversification. To type A-1 belong the cases where first horizontal consolidation of single-unit-firms took place because the high percentage effect brought about severe competition and then vertical integration evolved, and no incentive to diversification existed. In type A-2 the percentage effect was low and other conditions were similar to those in type A-1. In type B-1 one firm began vertical integration and a few firms followed it, and then the severe competition between them led to horizontal consolidation. There, the percentage effect was high because vertically integrated firms became standard, and incentive to diversification was little. In type B-2 incentive to diversification was an important factor that led to consolidation, and other conditions were similar to those in type B-1. These four types express the dynamism of American industry in this period. The cases in type A-1 were in the main stream where the progress in technology itself gave birth to overproduction. In type B-1 where the technological condition was similar to type A-1, innovations made pioneers develop new strategies (vertical integration). The cases in type A-2 show the move to consolidation in the low-technology industries. The cases in type B-2, though only a few, imply the emergence of new type of industries where product-innovation is of significance. After consolidation most of the large corporations in every type began to pursue the strategy of growth through diversification which was still of narrow range in most cases.