Frederic Milton Thrasher (1892–1962) taught sociology at the University of Chicago and was a prominent member of the first Chicago School of Sociology. His 1925 doctoral dissertation became the basis of The Gang: A Study of 1,313 Gangs in Chicago. Later he was a professor of educational sociology at New York University.
Thasher's “Chicago Gangland Map” from the 1920s is available online
from the University of Chicago Library.