Over the past two decades, U.S. states have widely adopted early literacy policies. These policies have shown short-term success in enhancing K-3 literacy skills. However, the reasons behind their widespread adoption and the factors driving their success are poorly understood. This three-paper dissertation focuses on Michigan's Read by Grade Three Law, enacted in 2016, to delve into the adoption and implementation of these policies. The Read by Grade Three Law is an informative case study because it is one of the U.S.'s most comprehensive early literacy policies. The first paper employs interviews and policy document analysis to explore the law's adoption and the dissemination of early literacy policies across states, highlighting the significant role of policy entrepreneurs. The second and third papers examine the policy's implementation, specifically its family engagement requirement and districts' methods to identify students with "reading deficiencies." The second paper analyzes data from the Michigan Department of Education and educator surveys spanning 2019-2023, uncovering that only 20% of eligible students receive "Read at Home" family engagement plans. The findings highlight considerable differences among districts and demonstrate how educators' understanding and perceptions are closely linked to the execution of these plans. The third paper uses superintendent survey data and state records from the 2021-22 school year to investigate how districts identify students with "reading deficiencies," making them eligible for supports such as "Read at Home" plans. The results reveal that districts use diverse measures to identify students. These variations are related to significant disparities in identification rates, with implications for which students receive literacy support under the Read by Grade Three Law. Together, these studies illuminate the complexities of policy adoption and implementation, enhancing our understanding of early literacy policies and laying the groundwork for future research on their mechanisms of success. [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://bibliotheek.ehb.be:2222/en-US/products/dissertations/individuals.shtml.]