Network structure varies across cities. This variation may yield important knowledge about how the internal structure of the city affects its performance. This paper systematically com- pares a set of surface transportation network structure variables (connectivity, hierarchy, circuity, treeness, entropy, accessibility) across the 50 largest metropolitan areas in the United States. It finds most of these measures vary with city size. A set of scaling parameters are discovered to show how network size and structure vary with city size. These results suggest that larger cities are physically more inter-connected.