He was a colleague of Robert E. Park and was one of the most prominent members of the Chicago School of Sociology in the 1920s.
Thrasher’s work on gangs was one of a series of outstanding doctoral studies completed under Robert E. Park’s direction in the "golden era" of the University of Chicago Sociology Department.
"Isolation is common to almost every vocational, religious or cultural group of a large city.
Each develops its own sentiments, attitudes, codes, even its own words, which are at best only partially intelligible to others."
His courses on the subject were path breaking, including a course, begun in 1934, named “The Motion Picture: Its Artistic, Educational and Social Aspects.” He also served widely as a consultant to groups concerned with motion pictures, crime, prison reform, and prevention of juvenile delinquency.