This paper reviews the sources of and potential solutions to teacher shortages in the United States. It describes the sources of current and projected increases in teacher demand relative to enrollments, shifts in pupil-teacher ratios, and attrition. It places these in relation to recent declines in teacher supply and evaluates evidence of shortages in fields like mathematics, science, special education, and educators for English learners, as well as in particular parts of the country. Our analysis using national databases through 2016 predicted an estimated annual teacher shortage of approximately 112,000 teachers in 2017-18. Our recent review of state teacher workforce reports estimated 109,000 individuals were uncertified for their teaching positions in the US in 2017, roughly approximating our projections. We discuss the factors driving shortages and, based on previous research, identify responses that might ameliorate these trends.