BACKGROUND: As of 2021, at least 4 out of every 5 hospitals offered patients access to clinical notes via a web-based patient portal, a number that is expected to grow because of the 21st Century Cures Act. There is limited data on how open note use may have evolved over time or which types of clinical interactions were viewed most in the outpatient setting. OBJECTIVE: This study aims to analyze trends in outpatient open note access over time; characterize usage in terms of age, sex, and clinical interaction type; and assess the method of access to help uncover areas of improvement in patient engagement and identify further areas of research. METHODS: A retrospective observational study was conducted at Erie County Medical Center from November 1, 2021, to December 31, 2022, to coincide with the time that open notes went live. Outpatient note access and account logs were downloaded from the portal and combined into a single dataset consisting of 18,384 note accesses by 4615 users, with column headings of the patient index, sex, age, note title that was accessed, clinical interaction type, time stamp of note creation, time stamp of access, and method of access (web vs mobile). A separate table was created with sex data for all 35,273 portal accounts. Microsoft Excel and Microsoft Power Query were used to combine and analyze the data. RESULTS: During the study period, 4615 portal users viewed 12,150 documents for a total of 18,384 times, averaging 2.6 notes per patient viewed 4 times. Only 13.1% (4615/35,273) of all portal inpatient and outpatient registrants viewed their outpatient notes. There was a female predominance in those who viewed notes (2926/4615, 63.4%; P<.001), while 56.8% (20,047/35,273) of all portal registrants were female. Users in their 30s and 50s accessed more notes than other age groups. The ratio of mobile-to-web access of notes tended to decrease as a function of increasing age, which was not observed in those aged ≥90 years. Notes regarding COVID-19 assessments were the most accessed among all clinical interactions (4725/12,150, 38.9%). Overall, the number of users accessing notes reached a maximum of 1968 before declining to 1027 by the end of the study period. CONCLUSIONS: Open note access was largely dominated by COVID-19 assessments, and the number of users viewing their notes has declined over time as the pandemic subsided. Furthermore, female patients and those aged in their 30s as well as 50s viewed more notes than other groups. Finally, the percentage of notes viewed via a mobile device tended to decrease as a function of increasing age, showing that web-based access of open notes is an important modality for older patients.