Hazards in the urban built environment can create barriers to mobility among older adults aging in place. We investigated the relationship between urban built environment characteristics and 15-month trajectories of mobility disability in a sample of 1,188 older adults living in Detroit, MI, a city that has undergone rapid economic and structural decline. Data come from the Michigan Minimum Data Set for Home Care (2001-2008), an enumerative database of older adults in Michigan who qualify for federal or state-funded home and community-based long-term care through a Medicaid waiver program. Standardized assessments are made at intake and every 90 days by case managers. Built environments were assessed with a virtual audit using the "Street View" feature of Google Earth. A summary accessibility score was created for each block based on a count of the number of accessible features (e.g., continuous barrier-free sidewalks and proximity of public transportation). Using growth mixture models, two latent trajectories of outdoor mobility were identified: one capturing occasional outdoor mobility (representing 83 % of the sample) and one capturing almost no mobility outside the home. Controlling for sociodemographic and health risk factors, individuals living in more accessible environments had a 18 % higher odds of being in the more mobile group (OR = 1.18, 95 % CI = 1.01, 1.41). These findings emphasize the importance of the built environment for mobility among urban-dwelling older adults.