Carl Hempel
Hempel was active in Berlin on the heyday of logical empiricism, but settled in Brussels in 1934, and then moved to the United States in 1939. He soon became one of the most influential philosophers in the United States. Analyses of confirmation, of explanation, of theoretical terms, and of reduction are among his important contributions; in particular, the contemporary discussions of scientific explanation all refer back to Hempel's famous 1948 paper (with Oppenheim). The so-called "standard view" of philosophy of science in the 50's and early 60's contains Hempel's view at its core.
Hempel's influence is quite widespread, not confined to the so-called standard philosophy of science, centering on physics and related fields. His theory of explanation was extended to social sciences, and Hempel was in fact one of the leading figures of "naturalism" (the position that holds that social sciences can be conducted in the same manner as natual science) in the philosophy of social sciences. His analysis of functional analysis and functional explanation (explanation of the persistence of a certain feature in a society or in an organism in terms of its function) set a standard which any serious discussion of functional explanation must take into account.
He raised many philosophers at Princeton (since 1955), and he was known as "Peter" among his friends and associates.
See also "Hempel" in Internet Encyclopedia of Philosophy