Starting in 1925 she was music and drama critic for The Journal of Commerce. She was so well known for giving caustic reviews to what she considered bad performances that she earned the nickname "Acidy Cassidy." According to a 1993 article by the Chicago Reader, Rafael Kubelik, was "practically hounded out of town" by Cassidy. Cassidy had a particular aversion to touring companies of Broadway shows.
Although she was known for her harsh criticism, Cassidy's enthusiasm may have been even more powerful. According to Philip Rose, A Raisin in the Sun became a hit after a surprise positive review from Cassidy as well as "good reviews in other papers." In 1975, Cassidy was awarded the Joseph Jefferson Award. Her last published writing was for the 1990-91 Lyric Opera program book.
- Grimes, William (1996-07-27). "Claudia Cassidy, 96, Arts Critic; Did Not Mince Words in Chicago". The New York Times. ISSN 0362-4331. Retrieved 2017-01-18.
- Jones, Chris (2013-10-04). Bigger, Brighter, Louder: 150 Years of Chicago Theater as Seen by "Chicago Tribune" Critics. University of Chicago Press. ISBN 9780226090719.
- Shen, Ted. "Under the Gun". Chicago Reader. Retrieved 2017-01-18.
- "Obituaries". Backstage.com. Retrieved 2017-01-18.
- Rose, Philip (2001-01-01). You Can't Do that on Broadway!: A Raisin in the Sun and Other Theatrical Improbabilities : a Memoir. Hal Leonard Corporation. ISBN 9780879109608.
- "Claudia Cassidy Theater at the Chicago Cultural Center, The Loop | Metromix Chicago". chicago.metromix.com. Retrieved 2017-01-18.