Apart from a few articles, no comprehensive study has been written about the learned men and women in America with Czechoslovak roots. That's what this compendium is all about, with the focus on immigration from the period of mass migration and beyond, irrespective whether they were born in their European ancestral homes or whether they have descended from them. Czech and Slovak immigrants, including Bohemian Jews, have brought to the New World their talents, their ingenuity, their technical skills, their scientific knowhow, and their humanistic and spiritual upbringing, reflecting upon the richness of their culture and traditions, developed throughout centuries in their ancestral home. This accounts for the remarkable success and achievements of these settlers in their new home, transcending through their descendants, as this monograph demonstrates. The monograph has been organized into sections by subject areas, i.e., Scholars, Social Scientists, Biological Scientists, and Physical Scientists. Each individual entry is usually accompanied with literature, and additional biographical sources for readers who wish to pursue a deeper study. The selection of individuals has been strictly based on geographical ground, without regards to their native language or ethical background. This was because under the Habsburg rule the official language was German and any nationalistic aspirations were not tolerated. Consequently, it would be virtually impossible to determine their innate ethnic roots or how the respective individuals felt. Doing it in any other way would be a mere guessing, and, thus, less objective.