This paper examines the dramatic changes to city block morphology that occurred during the 20th century in Detroit, MI, USA. The study area is comprised of four square miles (10.4km2) of downtown Detroit. The paper measures the amount and causes of city block frontage change between the years 1896 and 2002, and finds that 37% of Detroit’s 1896 city block frontage was removed by 2002. Only 50% of the removed frontage was replaced with new frontage. The city block changes indicate a consistent replacement of small blocks and their intervening streets with larger superblocks with few or no cross streets. Almost 50% of city block frontage removal was attributable to slum clearance or ‘urban renewal’ and highway (motorway) construction. Smaller amounts of block reconfiguration were due to large-scale building (megaproject)
construction, street widening, and block consolidation for industrial, institutional, and parking-related uses. The recent city block restructuring resulting from new megaprojects indicates that the further replacement of Detroit’s 19th-century street and block structure by superblocks is likely.