Walkability relates to aspects of a physical environment that have the potential to influence walking in that environment. In 2019, the Environmental Protection Agency developed the National Walkability Index (NWI), an easily accessible, U.S. Census block-group-level indicator of walkability. Although the NWI could be the metric of choice for researchers and urban planners, there is a lack of empirical evidence for its validity. The current study examined the validity of the NWI and Walk Score for predicting physical activity (PA) occurring along urban streetscapes. A wearable video device (Gogloo E7 SMART eyewear) was used to capture videos of streetscapes in 24 U.S. Census block groups in three different sized cities. The block groups varied in walkability, income level, and minority composition. The videos, collected over 10 months during 2019 at different times on weekdays and weekends, were reviewed by experts to obtain counts of walkers/h and individuals performing leisure PA/h (dependent variables). The independent variables were the NWI, its components - transit stop proximity, intersection density, employment/household occupancy mix, and employment mix, and Walk Score. Block group was the level of analysis. Linear regression indicated Walk Score, employment/household occupancy mix, and employment mix were associated with walkers/h (p < .001) while only employment/household occupancy mix, and employment mix were associated with leisure PA/h (p < .001). The NWI did not account for a significant portion of the variance in PA outcomes. A place-based examination of PA and walkability indexes favors the use of Walk Score and a modified version of the NWI.