AbstractOne of the fundamental inputs to models of population exposure to the power‐frequency fields of high‐voltage transmission lines is the density of population about the lines. We examined aerial photographs of over 1,700 km of transmission corridor to characterize the density of nearby housing units. The data show that the density of houses within 200 m of transmission lines (1) is typically smaller than the average density of houses in the local utility's service area, (2) tends to increase with distance from the line, and (3) is inversely correlated with line volt