This study reports that all three of the fundamental characteristics of a street network—street connectivity, street network density, and street patterns—are statistically significant in affecting the choice to drive, walk, bike, or take transit. Both increased intersection density and additional street connectivity were generally associated with more walking, biking, and transit use. Street patterns with gridded street networks, which tended to have a higher-than-average street connectivity and a much higher street network density, were associated with much more walking and biking. These results suggested that street network patterns were extremely important for encouraging nonautomobile modes of travel. As the United States begins to focus on reducing vehicle miles traveled as a strategy to combat carbon production and cut energy use, it is increasingly imperative that this relationship between the built environment and mode choice be accounted for in the planning and design of the transportation system.