Educational resources in mathematics are an important aspect of the teaching and learning landscape. Moreover, resources have come a long way from the spoken word with such inventions as paper and the computer to the point where there is now an infrastructure around open educational resources (OER) that has matured into viable alternatives to traditional resources. The newfound prevalence of these materials provides opportunities to customize OER to the specific needs of students and institutions. We designed open source material for the social science strand of differential and integral calculus by adopting an open source textbook and adapting it for our needs. Along with the course notes, we developed lecture notes, student notes based on the Cornell note-taking system, and assignments with solutions. Students are appreciative of free material, but moreover, the cohesiveness and interconnectivity among the various course materials provides for a smoother learning journey through our courses. This paper presents our philosophy, an overview of our open source material, and the operation of both courses.