Navigating a career in illustration can be very difficult, due to a lack of structure and traditional academic writing in the field. This is especially true for visual trends. While a plethora of histories are available, traditional data is limited. The thesis for this study seeks to address this issue: Identifying and categorizing illustration trends by defined visual characteristics will provide data for classroom instruction and guidance for professionals while strengthening a burgeoning field of research in illustration and developing an ongoing tool for understanding the industry. The study begins with a review of literature that examines the current field of illustration research, then compares it to similar fields. Next it looks at possible causes for trends in general, and finally how illustration is categorized across the field. The methodology applied to the study is a mixed-methods approach using a developed set of tools that categorize thousands of images published over several decades in the Society of Illustrators Annuals into visually different types of illustration. The study lays down markers for future research and adds data to what was previously seen in an observational sense. This opens up the way for future research aimed at replicating this study or examining other illustration data points going further back in time. Results discussed in the paper include distinct, substantial periods of time of popularity for the different types of illustration found in the study, with minor exceptions. This mostly confirms the thesis, with the modification that long-term cycles could not be proven by the data, leaving hard conclusions somewhat open-ended for now.