Abstract: This paper studies the impact of several factors on the geographical distribution of basic scientific research across countries and time, and explains the dynamics of the process that has resulted in the United States becoming the undisputed leader in basic research. Our study is based on the records of major scientific awards, and on data dealing with global economic and historical trends. We investigate the degree to which scale or threshold effects account for the number of major prizes (Nobel, Fields, Kyoto, Wolf) won by different countries. We constructed a stylized model, predicting that lagged relative GDP of a country relative to the GDP of all countries engaging in basic research is an important explanatory variable of a country?s share of prizes. Scale effects imply that the association between the GDP share of a country and its prize share can be logistic -- above a certain threshold, there is a take-off range, where the prize share increases at an accelerating rate relative to the GDP share of the country, until it reaches "maturity" stage. Our empirical research findings confirm the importance of lagged relative GDP in accounting for a country's prize shares, and the presence of a "winner-takes-all" scale effect benefiting the leader. We found that U.S. basic research take-off started during the 1920s, with this research being done in the United States by U.S. scholars, prior to the immigration of scientists after Hitler's rise to power in Germany (1932-33). This is consistent with the notion that World War II set in motion forces that did not start, but hastened, the U.S. take-off, triggering immigration that contributed to the speed and intensity of U.S. research dominance. Using more recent data, we also documented the growing importance of countries that used to be at the periphery of global research, but are now possibly advancing towards the take-off stage.