For most of her life, Claudia Cassidy (1899–1996) was Chicago’s most prolific and widely read critic, and, as this paper argues, one of the most influential arts critics of the twentieth century. She began her career at the Chicago Journal of Commerce (1924–1941), moving from there to the Chicago Sun (1941–42) and then to the Chicago Tribune (1942–65), where she reached the height of her influence. After leaving the Tribune, Cassidy wrote for numerous local and national publications as a critic-at-large. In total, her career spanned five beats (music, theater, dance, books, and film), two continents (North America and Europe), and nearly seven decades, giving her a uniquely privileged vista of the twentieth century’s performing arts. However, Cassidy has been largely neglected in academia and greater discourses about American arts criticism since her death. This paper launches the first analysis of the legacy and local impact of Cassidy’s music criticism, positing Cassidy’s ability to reach wide audiences at the Tribune, her colorful writing style, and advocacy for Chicago’s arts as primary factors in her rise. By consulting oral histories and personal correspondences, as well as Cassidy’s own work, this paper also disentangles the complexities of Cassidy’s legacy, addressing assertions made against her: for example, that she was guilty of gross conflicts of interest, that she was musically naïve, and that her criticism was especially vitriolic. Specific episodes in Cassidy’s career are addressed as touchstones, including her involvement with Lyric Opera as it reemerged in the 1950s, her varying approval of CSO leadership, and her departure from WFMT after general director Norm Pellegrini threatened to dismiss her over her CSO coverage. These conflicts are foregrounded to highlight Cassidy’s unique influence on Chicago institutions. This paper was published in the Chicago Studies Annual (2018) and was the recipient of the University of Chicago Music Department's Leonard B. Meyer Thesis Prize.