The School of Education and the Department of Physics at Boston University offer a sequence of 10 two-credit professional development courses through the Improving the Teaching of Physics (ITOP) project. The ITOP courses combine physics content, readings from the physics education research (PER) literature, and the conceptual history of physics (CHOP). ITOP participants self-report changes to their teaching practices as a result of their participation in ITOP. The purpose of this study was to verify and characterize those changes in the specific area of the participants' use of history after their study of CHOP. Ten recent ITOP participants were observed, interviewed, and asked to provide lesson plans and samples of student work from their classes. Case studies of each participant's teaching were constructed from the data. The individual cases were synthesized to characterize the impact of CHOP on the ITOP participants. The results show that the participants integrate CHOP into their pedagogical content knowledge (PCK) to inform their understanding of: (1) the relationship between physics and other disciplines, (2) the relationship between specific physics concepts, (3) student understanding of physics concepts, (4) student difficulties in learning physics concepts, and (5) methods for teaching physics concepts. The participants use history to teach a variety of topics, although the most common were mechanics and electromagnetism. All of the participants used history to teach aspects of the nature of science (NOS) and to increase student interest in physics, while eight participants taught physics concepts through history. The predominant mode of incorporating history was through adding anecdotes about the scientists who worked on the concepts, but seven participants had their students study the historical development of physical concepts. All the participants discussed a lack of time as a factor that inhibits a greater use of history in their courses. Eight participants discussed a lack of appropriate resources for using history in high school physics classes. Two participants said they did not feel that explicit study of the history of physics would benefit their students until they had better mastery of physics concepts. [The dissertation citations contained here are published with the permission of ProQuest LLC. Further reproduction is prohibited without permission. Copies of dissertations may be obtained by Telephone (800) 1-800-521-0600. Web page: http://www.proquest.com/en-US/products/dissertations/individuals.shtml.]