The Day 1 Academies Fund aims to support a network of high-quality, full-scholarship, Montessori-inspired preschools in underserved communities. To provide insight into the fund's pedagogical inspiration, in this report I provide a high-level overview of the Montessori preschool landscape in the United States. This overview includes 5 key programmatic elements of a traditional Montessori approach to teaching and learning in classrooms serving preschool-aged children, the reported availability of Montessori programs that enroll 3- and 4-year-old children, and what is known about enrollees' demographics. To situate this information in the larger, publicly financed, early education policy context, I also provide similar data for state-funded pre-K and federally funded Head Start programs for preschoolers. In addition, I review research on children's outcomes after participating in U.S.-based Montessori preschool and elementary programs. This overview provides some context for understanding how the Day 1 Academies Fund eventually defines the constructs of high quality, Montessori inspired, and underserved. This review also suggests it could be useful for the Fund's stakeholders to undertake short-term research examining the current early education options of families with low incomes living in potential low-access-to-Montessori states as well as long-term research aimed at expanding the research base on the effects of Montessori programs aimed at preschoolers.