3Madison Grant's controversial work, which advances the idea of a superior Nordic race, was published at a time when immigration to the United States was at a historic high.

As a eugenicist, Madison Grant believed that it was necessary for the USA to initiate a breeding program, that the original white Protestant settlers not lose their heritage and culture. For the author, the rapid increase in populations of Southern and Eastern Europeans, plus other races, would undermine, corrupt or even destroy the United States.

The book commences by proscribing a social manifesto to address the marginalization of the original white populations. Grant concludes that without a eugenics program the historically modest breeding records of the original colonialists, coupled with the high numbers of non-Nordic immigrants, would render the original population effectively extinct within a few decades.

The second, lengthier part of the book is Madison Grant's history upon the races of humanity. His theory concerns a differentiation of characteristics, identifying how the Mediterranean, Alpine and Nordic peoples behave distinctly. Finally the theory of the Aryan peoples and their origins is advanced.

Since its original publication in 1916, the manual has been repudiated for its attitudes regarding race. The ideas Grant espouses regarding eugenics fell out of favor in the USA by the 1930s, and in Europe following the Second World War. Modern scientists and historians consider this work to be among the foremost examples of scientific racism of the 20th century.