Closing the teacher diversity gap is one of the most important steps we can take to make public education more equitable. But as many school systems across the country have prioritized the issue, one institution has largely escaped scrutiny: teacher preparation programs. In this report, we use data from the U.S. Department of Education to compare the demographics of each state's teacher preparation program enrollees to that of public school students to calculate a "teacher prep diversity gap." We also highlight individual teacher preparation programs that are--and are not--recruiting enough teachers of color to match student demographics in their states. Findings include: (1) Teacher preparation programs are significantly whiter, on average, than the public school population; (2) Teacher prep diversity gaps exist in almost every state; (3) A significant percentage of programs--serving a significant number of future teachers--are more than 90 percent white; and (4) Alternative certification programs are significantly more diverse than traditional programs. We also provide a series of recommendations for programs, districts, and state governments. We are in no way suggesting that teacher preparation programs are solely responsible for the shortage of teachers of color. But to address this problem, all parties involved--from the state and federal government, to teacher preparation programs, to districts--need to commit to and be held accountable for doing better. We hope this paper can help start conversations across the country on an important topic, and hopefully encourage education leaders to make diversifying the teaching profession a top priority.