This brief provides a summary of the results of a project designed to help build the collective capacity and increase the impact of programs working to improve K-3 reading outcomes in New York City public elementary schools (the "K-3 reading improvement sector"). The first phase of this project identified all of the programs working in the sector in 2015 and then examined the extent to which a sample of programs have the goals, resources, personnel to improve K-3 reading outcomes across New York City. In 2016-17, the second phase of this project mapped the relationships among a sample of sector programs, the sources they rely on to support their work, and the NYC schools with whom they partner. Making these relationships visible shows to what extent students from different backgrounds and schools get access to valuable information, resources, and expertise, and the extent to which programs are in a position to increase their collective impact through coordination and collaboration. [To view the full report, "Mapping the Reading Improvement Sector in New York City: The Role of External Support Providers in Improving K-3 Reading Outcomes," see ED597882. Additional support from the Brooke Astor Fund for New York City Education.]