The built environment may shape walking habits among older women. This study was designed to address the gaps in literature related to quantifying the built environment in order to investigate the association between the built environment and walking. Standardized and high resolution geographic units were established to objectively measure built environment attributes, and subsequent use of cluster analysis to assess the mixed effect among built environment attributes facilitated the examination of the association between urban forms and walking among women 65 years or older residing in the Portland metro area.