Since the early 20th century, inventors have conceptualized “plane cars” and other urban aerial transportation. Emerging innovations in electrification, automation, and other technologies are enabling new opportunities for on-demand air mobility, business models, and aircraft design. Urban air mobility (UAM) envisions a safe, sustainable, affordable, and accessible air transportation system for passenger mobility, goods delivery, and emergency services within or traversing metropolitan areas. This research employed a multi-method approach comprised of 106 interviews with thought leaders and two stakeholder workshops to construct the history, ecosystem, state of the industry, and potential evolution of UAM. The history, current developments, and anticipated milestones of UAM can be classified into six phases: 1) “flying car” concepts from the early 1910s to 1950s, 2) early UAM operations using scheduled helicopter services from the 1950s to 1980s, 3) re-emergence of on-demand services starting in the 2010s, 4) corridor services using vertical take-off and landing (VTOL) envisioned for the 2020s, 5) hub and spoke services, and 6) point-to-point services. In the future, UAM could face several barriers to growth and mainstreaming, such as the existing regulatory environment; community acceptance; and concerns about safety, noise, social equity, and environmental impacts. UAM also could be limited by infrastructure and airspace management needs, as well as business model constraints. The paper concludes with recommendations for future research on sustainability, social and economic impacts, airspace integration, and other topics.