Elementary school students' knowledge of history appears to be at an all-time low as evidenced by the 2010 NAEP scores that indicated only 20% of fourth-grade students scored at the "at least proficient" level in a test of historic knowledge. Many culprits are being blamed for this dismal performance of U. S. students, such as No Child Left Behind's (NCLB) lack of emphasis on history, teachers' lack of training in teaching history, traditional textbook use in teaching history, and society's general apathy toward history and civics. The U.S. Department of Education attempted to improve students' historic knowledge in 2001 by creating the Teach American History (TAH) grant program, which promoted school district/university collaboratives intended to increase K-12 teachers' historic knowledge and improve their classroom practices. Research over the past decade has grown substantially regarding the need for teachers and students to think historically rather than just learn historic facts. Increasing historical thinking has been a goal of TAH projects around the country. This study investigated three fifth-grade teachers involved in a TAH project in Utah. Teachers were interviewed in their classrooms and observed in TAH settings in an attempt to determine the growth of these teachers' historical thinking and how this growth might affect their classroom instruction. The results indicated that these teachers reported learning to think historically and improving their classroom practices substantially through this TAH socially mediated professional development. These teachers also reported evidence that the historical thinking of their students had improved. Findings indicated that the characteristics of historical thinking were discussed in this TAH project but not necessarily in depth. The three teachers' understanding of what is involved to think historically remains somewhat vague. [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.]