Background/Question/Methods Urban forested natural areas contribute to improving the livability and sustainability of cities. However, urbanization has environmental consequences that can lead to declines in tree canopy, introduced species, and the degradation of forest condition. Yet there is little information about the scale of natural areas in cities and their management systems. We used data sets on city parkland from across the United States and surveyed practitioners to understand urban natural area forest extent, ecosystem services and management. First we asked how urban natural area parkland changed in 100 US cities over a 5 year period. Then using an online survey we asked over 100 U.S. cities about their forest management goals, challenges and outcomes. Finally, we used four cities as a case study to calculate carbon storage and sequestration of urban natural areas. This study highlights an emerging field of common forest management strategies adapted to dealing with urban situations that could lead to best management practices for complex human-impacted forest ecosystems. Results/Conclusions We find that urban natural areas are a dominant greenspace land cover, accounting for 68% of total city parkland across 96 of the most populous cities in the United States in 2019. Over a five-year period (2014–2019), natural area parkland decreased by 4% (15,264 hectares) in these cites. At municipal scales, most cities are managing forested natural areas to conserve native species, and many different management interventions are being used to steer forest structure and composition. These activities and their outcomes are being tracked nearly 70% of the time by the managing organizations, suggesting a strong data basis for adaptive management. However, challenges exist: 94% of organizations cite invasive species and limited funding as primary challenges. Lack of data and low public awareness of the value of natural areas are also considered primary challenges by more than 70% of the organizations surveyed. Protecting natural area parkland from development and addressing the challenges managers of these ecosystems face are two very important goals. We found that the majority of carbon stored in trees in selected cities is found in urban natural areas despite being a minority of total tree canopy. We then describe the emergent Forests in Cities program: a 12-city network collaborating and co-producing knowledge with the goal of promoting and advancing healthy forested natural areas in cities across the United States through science, management, partnerships, and communications.