To be an informed citizen in today's information-rich environment, individuals must be able to evaluate information they encounter on the Internet. However, teachers currently have limited options if they want to assess students' evaluations of digital content. In response, we created a range of short tasks that assess students' "civic online reasoning"--the ability to effectively search for, evaluate, and verify social and political information online. Assessments ranged from paper-and-pencil tasks to open Internet search tasks delivered via Google Forms. We outline a process of assessment development in which middle school, high school, and college students in 12 states completed tasks. We present a series of representative tasks and analyses of trends in student performance. Across tasks and grade levels, students struggled to effectively evaluate online claims, sources, and evidence. These results point to a need for curriculum materials that support students' development of civic online reasoning competencies.