No doubt the Mexican Indian is well suited to his environment, and his traditional habits are well suited to him. This does not mean, however, that either has any important contribution to make to the United States which would be realized by a northward mass migration of agricultural and industrial serfs. On the contrary, the Mexican immigration to the United States, which is made up overwhelmingly of the poorer Indian element, has brought nothing but disadvantages.

The Conquest of a Continent (1933)